Tropical Land Research Articles

Stronger Response to the Aerosol Indirect Effect Due To Cooling in Remote Regions.

It is often assumed that effective radiative forcings, regardless of forcing agent, are additive in the temperature change. Using climate model simulations with abruptly applied aerosol forcing we find that the temperature response per unit forcing is larger if induced by aerosol-cloud interactions than directly by aerosols. The spatial patterns of forcing and temperature change show that aerosol-cloud interactions induce cooling over remote oceans in the extratropics, whereas the effect of increased emissions is localized around the emission sources primarily over tropical land. The results are consistent with ideas of how the patterns of sea surface temperature impact radiative feedbacks, and a large forcing efficacy of aerosol-cloud interactions could help explain previously observed intermodel spread in the response to aerosols.

Meridional Propagation of Carbon Dioxide (CO2) Growth Rate and Flux Anomalies From the Tropics Due to ENSO

AbstractEl Niño Southern Oscillation (ENSO) influence on carbon dioxide (CO2) growth rates are not spatially uniform or simultaneous around the globe. Using atmospheric CO2 observations and atmospheric chemistry‐transport model (ACTM), we show that anomalies in CO2 fluxes and growth rate originate in the tropics, as an effect of ENSO. The CO2 anomalies are then propagated from the equator toward the poles with asymmetric delays. A maximum delay of about 8 and 4 months are found at the northern hemisphere (NH) and southern hemisphere (SH) high latitudes, respectively. This asymmetric time delay is because of the CO2 flux anomaly mainly originate in the tropical SH land and transport of SH air into the NH is slower than that for NH air into the SH. The poleward increase of time delay is more homogeneous in the upper troposphere, as per the ACTM simulations, but observational evidence suffers from gaps in long‐term measurements.

Evaluation of tropical water vapour from CMIP6 global climate models using the ESA CCI Water Vapour climate data records

Abstract. The tropospheric water vapour data record generated within the ESA Climate Change Initiative Water Vapour project (ESA TCWV-COMBI) is used to evaluate the interannual variability of global climate models (CMIP6 framework under AMIP scenarios) and reanalysis (ECMWF ERA5). The study focuses on the tropical belt, with a separation of oceanic and continental situations. The intercomparison is performed according to the probability density function (PDF) of the total column water vapour (TCWV) defined yearly from the daily scale, as well as its evolution with respect to large-scale overturning circulation. The observational diagnostic relies on the decomposition of the tropical atmosphere into percentile of the PDF and into dynamical regimes defined from the atmospheric vertical velocity. Large variations are observed in the patterns among the data records over tropical land, while oceanic situations show more similarities in both interannual variations and percentile extremes. The signatures of El Niño and La Niña events, driven by sea surface temperatures, are obvious over the oceans. Differences also occur over land for both trends (a strong moistening is observed in the ESA TCWV-COMBI data record, which is absent in CMIP6 models and ERA5) and extreme years. The discrepancies are probably associated with the scene selection applied in the data process. Since the results are sensitive to the scene selection applied in the data process, discrepancies are observed among the datasets. Therefore, the normalization process is employed to analyse the time evolution with respect to the mean state. Other sources of differences, linked to the models and their parametrizations, are highlighted.

Regime Changes in Atmospheric Moisture under Climate Change

Recent work attributing decadal regime changes in temperature to radiative forcing is extended to atmospheric moisture. Temperature, and specific and relative humidity (T, q, RH) from the HadISDH data set were analyzed for regime shifts using the bivariate test. Most shifts in q and T for global and northern hemisphere (NH), and tropical land occurred within a year of each other. Only one shift of q was recorded in the southern hemisphere (SH). RH increased in the NH in 1990–91 and decreased in a series of shifts from the late 1990s, while in the SH decreased from 2001. The tropics have remained neutral, shifting negative over land and positive over the ocean. The global decreases in 2001 and 2011 was −0.56%. Global RH from 32 climate models from the CMIP5 RCP4.5 archive all contained regime shifts but only 4 reached or exceeded the observed decreases by 2100, the earliest in 2056. Regime shifts in RH and fire danger over Australia are consistent with the SH decreases in RH, shifting within one year of global fire season length in 2002, showing that impacts are also being underestimated by current analyses. Methods for nonlinear attribution and the contributing processes for nonlinear change are discussed. These results show that developing a better understanding of nonlinear change in moisture-related climate risk is an urgent task.

Enhanced Interannual Variability in Temperature during the Last Glacial Maximum

Abstract Using all relevant climate experiments archived in phases 3 and 4 of the Paleoclimate Modeling Intercomparison Project (PMIP3/4), we examine the interannual variability change in global-scale surface air temperature and associated physical mechanisms during the Last Glacial Maximum (LGM). The results show that relative to the preindustrial period, the LGM interannual temperature variability increased by 20% globally, which was mainly attributed to the large-scale increase in the meridional temperature gradient, especially at midlatitudes. Larger magnitudes of change occurred in areas where the underlying surface properties, such as the surface altitude, land–sea distribution, and ice sheet extent, differed from those in the preindustrial period. In addition, the relationship between changes in the meridional temperature gradient and the interannual temperature variability became closer in the winter hemisphere. In the tropical land regions, changes in interannual temperature variability are mainly related to the adjustment of latent and sensible heat fluxes during the LGM.

Evolution of tropical land temperature across the last glacial termination

The tropical West Pacific hosts the warmest part of the surface ocean and has a considerable impact on the global climate system. Reconstructions of past temperature in this region can elucidate climate connections between the tropics and poles and the sensitivity of tropical temperature to greenhouse forcing. However, existing data are equivocal and reliable information from terrestrial archives is particularly sparse. Here we constrain the magnitude and timing of land temperature change in the tropical West Pacific across the last deglaciation using an exceptionally precise paleothermometer applied to a well-dated stalagmite from Northern Borneo. We show that the cave temperature increased by 4.4 ± 0.3 °C (2 SEM) from the Last Glacial Maximum to the Holocene, amounting to 3.6 ± 0.3 °C (2 SEM) when correcting for sea-level induced cave altitude change. The warming closely follows atmospheric CO2 and Southern Hemisphere warming. This contrasts with hydroclimate, as reflected by drip water δ18O, which responds to Northern Hemisphere cooling events in the form of prominent drying, while temperature was rising. Our results thus show a close response of tropical temperature to greenhouse forcing, independent of shifts in the tropical circulation patterns.

Bonanza o Falsas Riquezas: Cambiantes Imaginarios Mexicanos del Trópico y el Impulso Civilizatorio

Existing scholarship on “tropicality” emphasizes how Europeans and US-Americans constructed the tropics discursively and visually in the eighteenth and nineteenth centuries. Scientists, investors, and travelers denigrated tropical spaces to legitimize imperialism, labeling them backwards, racially degenerative, disease-ridden, and unconducive to civilization without white European intervention These works unwittingly reproduce a central assumption of the very imperialists they critique: namely, that North Atlantic elites controlled knowledge production. They thus marginalize the important theorizing and conceptualizing that transpired in tropical spaces. Following independence, Latin American national elites agonized over how to integrate their tropical territories, many of which remained isolated, and make them legible for economic modernization. This article uses Mexico as a case study for Latin American representations about the tropics given its diverse temperate and tropical geography, its key role in the global commercial economy, and its robust intellectual production. I argue that the ways in which Mexican intellectuals—public officials, geographers, philosophers, and others—thought about their low-lying tropical lands molded nation-building projects and contributed to the global production of environmental knowledge at a time when notions of tropical peril and degeneracy were giving way to the promise of tropical bonanza. By tracing the changes and continuities of Mexicans’ tropical discourses in a global context, I underscore the underappreciated environmental and geographic thought of influential Mexicans—from Matías Romero and Francisco Bulnes to José Vasconcelos—who rarely appear in environmental historiography. A focus on these different imaginaries regarding the significance, purpose, and place of Mexico’s tropical lands also reveals the extent to which material interventions in the tropics and discursive representations of the tropics have co-constituted each other.

Landscape conservation as a strategy for recovering biodiversity: Lessons from a long‐term program of pasture restoration in the southern Atlantic Forest

Abstract Although ecological restoration has entered the global agenda to reverse different anthropogenic disturbances, we still know little about how this solution interacts with other conservation strategies, to avoid the progressive loss of species and ecosystem services. Here we evaluate one of the pioneering restoration programs in the southern Brazilian Atlantic Forest, where the combination of conservation and restoration efforts has been carried out for 20 years. Specifically, we tested how landscape characteristics, restoration strategies and environmental characteristics affect the results of the restoration of pastures. We established 65 circular plots (total 4.0 ha) along restoration areas (3–10 years) and sampled trees and shrubs composing the canopy (DBH ≥ 5 cm) and understorey (DBH < 5 cm, height > 1.3 m). We analysed the landscape metrics (proportion of old‐growth forests in 200, 500 and 1,000 m buffers around each plot; and area and distance of the nearest‐neighbouring old‐growth forests). We explored the multiple effects of landscape, restoration strategy (reforestation, natural regeneration) and environmental variables (soil, pasture grass types) on the species composition and multiple diversity metrics of restoration areas. The species composition was very similar among restoration ages and restoration strategies. We found positive and strong effects of old‐growth forest (200 m buffer) proportion on the species richness and Shannon diversity (canopy and understorey), above‐ground biomass (canopy) and functional diversity (understorey) of restoration areas. The restoration strategies affected forest structure, and, in general, the reforestation strategy increased above‐ground biomass, Shannon, functional and phylogenetic diversities (in canopy), and percentage of endemic species and biomass (understorey), when compared to natural regeneration. The 20‐year experience in the southern Atlantic Forest showed that programs focused on landscape conservation associated with a mixture of restoration strategies (i.e. natural regeneration in larger areas and active restoration in more disturbed sites), can be an efficient strategy to ensure biodiversity and ecosystem services in tropical landscapes. Synthesis and applications. To manage degraded tropical lands and achieve global targets for biodiversity and ecosystem services, it is necessary to first ensure the conservation of natural remnants and then use multiple restoration strategies in less resilient areas.

Rising ecosystem water demand exacerbates the lengthening of tropical dry seasons

Precipitation-based assessments show a lengthening of tropical dry seasons under climate change, without considering simultaneous changes in ecosystem water demand. Here, we compare changes in tropical dry season length and timing when dry season is defined as the period when precipitation is less than: its climatological average, potential evapotranspiration, or actual evapotranspiration. While all definitions show more widespread tropical drying than wetting for 1983-2016, we find the largest fraction (48.7%) of tropical land probably experiencing longer dry seasons when dry season is defined as the period when precipitation cannot meet the need of actual evapotranspiration. Southern Amazonia (due to delayed end) and central Africa (due to earlier onset and delayed end) are hotspots of dry season lengthening, with greater certainty when accounting for water demand changes. Therefore, it is necessary to account for changing water demand when characterizing changes in tropical dry periods and ecosystem water deficits.

Tropical Continents Rainier Than Expected From Geometrical Constraints

AbstractAbundant rainfall over tropical land masses sustains rich ecosystems, a crucial source of biodiversity and sink of carbon. Here, we use two characteristics of the observed tropical precipitation distribution, its distinctive zonal arrangement and its partitioning between land and ocean, to understand whether land conditions the climate to receive more than its fair share of precipitation as set by the land‐sea distribution. Our analysis demonstrates that it is not possible to explain the tropics‐wide partitioning of precipitation unless one assumes that rain is favored over land. Land receives more than its fair share of precipitation by broadening and letting the tropical rainbelts move more, effectively underpinning a negative feedback between surface water storage and precipitation. In contrast, rain is disfavored over land in climate models. Our findings suggest that the abundance of rainfall that shapes the terrestrial tropical biosphere is more robust to perturbations than models have suggested.

Agroclimatic zoning of the state of Nayarit, México

Agriculture productivity in the state of Nayarit has decreased since 1998. The aim of the study was to undertake the agroclimatic zoning across the state in order to determine the type of crops more convenient to render the highest yields, based on Papadakis climate classification system. Hydric and thermal characteristics pertaining to the geographic distribution of crops were used, as well as indexes derived from meteorological data provided by 25 climate stations. There were three climatic groups identified: tropical, subtropical and cold land, having four, three and two subgroups each, respectively. First two climatic groups support winter cereals such as oat (Avena sativa L.), barley (Hordeum vulgare L.), rye (Secale cereale L.) and wheat (Triticum aestivum L.); and summer cereals such as corn (Zea mays L.), millet (Panicum italicum L.), rice (Oryza sativa L.) and sorghum (Sorghum bicolor (L.) Moench); in addition to banana (Musa paradisiaca L.), citrus and potato (Solanum tuberosum L.) and sugar cane (Saccharum officinarum L.). On the other hand, corn and potato were found in the cold land climatic group. Based on Papadakis’ methodology, for each climatic sub-group identified, a set of recommendation management were given to improve yields: crop type, sowing season, irrigation, fertilizing and other agrochemicals application; and to avoid crop damage. Agroclimatic zoning map was generated by using the inverse distance weighted interpolation method. This study may contribute to the successful planning of crops across the region and thus improving the state’s economy.

The Global Nature of Early‐Afternoon and Late‐Night Convection Through the Eyes of the A‐Train

AbstractCharacterizing macrophysical properties of deep convective systems on a global scale is a precursor to understanding their influence on Earth's Energy Budget and Water Cycle. This study documents the properties of global convective objects (COs) in the early afternoon (1:30 p.m. local time; LT) and overnight (1:30 a.m. LT) measurements from the A‐Train satellite constellation. CloudSat measurements are used to identify convective cores and establish their intensity, while other A‐Train data sets define cloud structure, storm spatial extent, rainfall yield, and radiative effects of each CO. Global distributions of storm characteristics are consistent with previous studies in which the most intense convection is located over tropical land, particularly over the Amazon and Congo Basin, while the largest COs occur over the Maritime Continent. Despite their limited twice‐daily sampling, A‐Train measurements capture that early afternoon convection over tropical land is both more intense and produces heavier rainfall than nighttime land‐based convection, while the day‐night differences are minimal over the tropical ocean. High‐resolution estimates of updraft cores reveal that CO size increases as the number of distinct cores in a CO increases owing to an increase in nonconvective rain and anvil cloud area. Convective objects generally cool the environment, which is strongest over the Northern Hemisphere midlatitudes, but cooling weakens as the nonconvective cloud fraction increases such that 30% of COs actually exert a net warming effect. These results suggest that A‐Train measurements may capture bulk connections between deep convective cloud features, precipitation, and radiative effects despite a lack of complete diurnal sampling.

Global Tropical Precipitation Relationships to Free-Tropospheric Water Vapor Using Radio Occultations

Abstract The transition to deep convection and associated precipitation is often studied in relationship to the associated column water vapor owing to the wide availability of these data from various ground or satellite-based products. Based on radiosonde and ground-based global navigation satellite system (GNSS) data examined at limited locations and model comparison studies, water vapor at different vertical levels is conjectured to have different relationships to convective intensity. Here, the relationship between precipitation and water vapor in different free-tropospheric layers is investigated using globally distributed GNSS radio occultation (RO) temperature and moisture profiles collocated with GPM IMERG precipitation across the tropical latitudes. A key feature of the RO measurement is its ability to directly sense in and near regions of heavy precipitation and clouds. Sharp pickups (i.e., sudden increases) of conditionally averaged precipitation as a function of water vapor in different tropospheric layers are noted for a variety of tropical ocean and land regions. The layer-integrated water vapor value at which this pickup occurs has a dependence on temperature that is more complex than constant RH, with larger subsaturation at warmer temperatures. These relationships of precipitation to its thermodynamic environment for different layers can provide a baseline for comparison with climate model simulations of the convective onset. Furthermore, vertical profiles before, during, and after convection are consistent with the hypothesis that the lower troposphere plays a causal role in the onset of convection, while the upper troposphere is moistened by detrainment from convection.

Analisis Faktor-Faktor yang Mempengaruhi Ekspor Crude Palm Oil (CPO) di Provinsi Kalimantan Selatan

This study aims to determine the factors that affect crude palm oil exports in South Kalimantan province, knowing the influence of production amount, dollar exchange rate, and CPO price on CPO exports in South Kalimantan Province. In increasing CPO production for the future, Indonesia is still superior because of the availability of sizeable tropical land for planting oil palm trees. Indonesia's CPO production, especially in South Kalimantan, continues to increase. It can be identified because of the influence of the amount of output, dollar exchange rate, and CPO price on South Kalimantan CPO exports?This research is research that uses multiple linear regression analysis techniques. Linear regression is one of the statistical tools used to describe the relationship between variables; the dependent and independent variables are used. The results showed that the amount of production (X1)) and the exchange rate of the Dollar (X3) together did not significantly influence the CPO Export of South Kalimantan (Y).

Soil carbon and microbes in the warming tropics

Abstract Climate warming could destabilise the Earth's largest terrestrial store of reactive carbon (C), by accelerating the decomposition of soil organic matter. A third of that C store resides in the tropics. The potential for tropical soils to sequester C, or to act as an additional source of CO2, will depend on the balance of C inputs and outputs, mediated by the response of soil microbial communities and their activity to perturbation. We review the impact of warming on microbial communities and C storage in humid tropical forest soils over multiple time‐scales. Recent in situ experiments indicate high sensitivity of tropical forest soil C mineralisation to warming in the short term. However, whether this will translate into long‐term soil C decline remains unclear. At decadal time‐scales, high sensitivity of soil C mineralisation to warming is consistent with the correlation between the inter‐annual variation in the tropical land surface temperature and atmospheric CO2 growth rate, and with simulations using the Carnegie‐Ames‐Stanford Approach biosphere model. This observed sensitivity may further contribute to climatic change over millennial time‐scales, suggested by radiocarbon dating of organic matter in river basins showing a twofold acceleration in tropical soil C release during the late‐glacial warming period. However, counter to this evidence, long‐term stability of tropical soil C is suggested by observed steady‐state soil C turnover across temperature gradients with elevation, and by the presence of C in tropical soils that pre‐dates the Holocene Thermal Maximum and late‐glacial warming periods. To help reconcile these recent experimental findings and long‐term observations, we propose mechanisms to explain tropical soil C and microbial responses to warming across multiple time‐scales. Combined in situ experimental and monitoring approaches—large‐scale and cross‐site—are urgently needed to resolve the interplay of these mechanisms across spatial and temporal scales, to shape a better understanding of the relationship between soil microbes and C storage in tropical soils. Read the free Plain Language Summary for this article on the Journal blog.

Native tree species richness enhances matrix functionality for soil arthropods in tropical plantation landscapes: A case study from the Himalayas

AbstractDespite their distinctive role in regulating agroecosystems, soil fauna is largely excluded from conservation action. With increasing evidence supporting matrix functionality as critical for multiple species in agroecosystems, it is important that efforts meant to enhance biodiversity in managed systems be inclusive and effective for all species and not just charismatic fauna.Third party certifications are a popular mechanism for claiming pro‐conservation practises in tropical agricultural lands. Therefore, we asked whether voluntary practises codified by third party certifications of tropical tea plantations support soil biodiversity, and what factors explain soil arthropod abundance and richness in such certified and uncertified landscapes.We used pitfall trap data and soil samples across two seasons in large tea plantations, and small tea‐growing agroforestry farms in the Darjeeling Himalayas in India. Plantations certified and those not certified were selected for the study.Soil arthropod morphospecies abundance, richness and diversity were significantly higher in summer as opposed to winter. Contrary to our expectations, there was no significant difference in soil arthropod abundance, richness and diversity between uncertified small agroforestry farms and certified large monoculture plantations. Our analysis establishes tree species richness and season as the most important predictors of soil arthropod abundance, richness and effective number of species.We recommend that increased abundance and diversity of native trees in the tea matrix should be a crucial criterion for agroecosystem management. This would improve matrix functionality for species that are sensitive to management and reflect practises that enhance biodiversity.

An Observational Analysis of a Persistent Extreme Precipitation Event in the Post-Flood Season over a Tropical Island in China

Featuring unique tropical land–sea contrast and mesoscale terrain, Hainan Island in China is endowed with active mesoscale convections of special regional characteristics. Persistent extreme precipitation events (PEPs) during the post-flood season, triggered by multi-scale interactions among mid-latitude and tropical weather systems, exhibit notable mesoscale features, long duration and high rainfall rates with low forecasting performance. This study is motivated by a failure to forecast a PEP in two stages with distinct characteristics and predictabilities, in the post-flood season over Hainan Island on 16–18 October 2020. Based on multiple sources of remote sensing and high-resolution rain gauge records, detailed observational analyses were conducted using a flow decomposition method. Water vapor divergence (WVD) and its three components were used to investigate the spatial distribution and temporal evolution of two stages with distinct characteristics and predictabilities during this PEP. Decomposed moisture components can be used to determine how and to what extent large- and sub-synoptic scale moisture convergence contributes to PEPs in the tropics, under similar synoptic backgrounds. Joint applications of multiple sources of remote sensing data and flow decomposed WVD are proposed to further assist predicting PEPs in terms of rainfall location and evolution.

Lessons from Brazil: Opportunities of Bioethanol Biofuel in Indonesia

Brazil has a long tradition of bioethanol production from sugarcane. Following the Middle East crisis in the 1970s, the oil price increased twofold, doubling Brazil’s spending on oil imports. As a result, the country had to find an alternative type of fuel to reduce its expenditure on conventional petrol fuels. With its vast tropical land conditions, the Brazilian government then put massive effort to establish the infrastructure and research of bioethanol from 1975 and 1989. Research plays a pivotal role in the success of Brazil’s ethanol industry. The country was heavily criticised at the beginning of the programme, but today, Brazil is the second-largest ethanol producer after the USA. Brazil produces the cheapest ethanol in the world and does not depend on fossil fuel to supply its energy demand. Indonesia and Brazil share the same landscape and geographical advantages. This paper aims to discuss the success of the Brazilian bioethanol industry and draw important lessons from it. In a nutshell, Indonesia should increase bioethanol production from renewable sources. Also, the modernization of distilleries facilities, the establishment of new production plants, the introduction of subsidies and the reduction of taxes for ethanol producers are needed. In summary, apart from massive research and development, we concluded that effective and strong long-term government commitment play important role in shaping the future of the Indonesian bioethanol industry.

Tropical land use alters functional diversity of soil food webs and leads to monopolization of the detrital energy channel.

Agricultural expansion is among the main threats to biodiversity and functions of tropical ecosystems. It has been shown that conversion of rainforest into plantations erodes biodiversity, but further consequences for food-web structure and energetics of belowground communities remains little explored. We used a unique combination of stable isotope analysis and food-web energetics to analyze in a comprehensive way consequences of the conversion of rainforest into oil palm and rubber plantations on the structure of and channeling of energy through soil animal food webs in Sumatra, Indonesia. Across the animal groups studied, most of the taxa had lower litter-calibrated Δ13C values in plantations than in rainforests, suggesting that they switched to freshly-fixed plant carbon ('fast' energy channeling) in plantations from the detrital C pathway ('slow' energy channeling) in rainforests. These shifts led to changes in isotopic divergence, dispersion, evenness, and uniqueness. However, earthworms as major detritivores stayed unchanged in their trophic niche and monopolized the detrital pathway in plantations, resulting in similar energetic metrics across land-use systems. Functional diversity metrics of soil food webs were associated with reduced amount of litter, tree density, and species richness in plantations, providing guidelines on how to improve the complexity of the structure of and channeling of energy through soil food webs. Our results highlight the strong restructuring of soil food webs with the conversion of rainforest into plantations threatening soil functioning and ecosystem stability in the long term.

The Effect of Light Distance on Aeroponic Potato Seed Production in The Tropical High Land

Aeroponic potato seed production in the highlands during foggy weather is an obstacle in increasing the number of tubers. Research that has been done previously is the addition of artificial light to support the growth and yield of potato seeds in the highlands. Nevertheless, from these results, there were still some plants that did not have optimal growth. It was suspected that the lamp height affects the growth and yield of aeroponic potato plants. The purpose of this study was to determine the effect of lamp distance on artificial lighting on the growth and yield of aeroponic potatoes. The factors that were tried were the height of the lamp from the aeroponic box 110 cm, 120 cm, and 130 cm. The lamps used: 18 Watt red blue LED (RB) and 10 Watt white fluorescent lamp. The design used was a completely randomized design. Growth observation data and results were analyzed by F test followed by Duncan's Multiple Distance Test (DMRT) 5%. The results showed that the combination of RB LED lamps with a height of 110 cm produced the highest number of bulbs of 31,7 per plant. The weight of aeroponic potato tubers in the highlands with the highest yield was obtained from a combination of 110 cm (29,3 g) RB LED lights. Keywords: Aartificial lighting, hydroponics, granola, greenhouse, tropical Indonesia