Long-Term Hydrological Research in the Humid Tropics

2022 ◽  
pp. 1-25
Author(s):  
Ian Douglas
Keyword(s):  
Humid Tropics

scholarly journals Tropical forest hydrology and the role of the UNESCO International Hydrological Programme

1999 ◽  
Vol 3 (4) ◽  
pp. 451-461 ◽  
Author(s):  
M. Bonell
Keyword(s):  
Land Use ◽  
Climate Variability ◽  
Tropical Forest ◽  
Focal Point ◽  
Humid Tropics ◽  
Cultural Dimensions ◽  
Forest Hydrology ◽  
Forest Land ◽  
North East

Abstract. The paper outlines a perspective on tropical forest hydrology within the context of an international hydrological programme. Experience in tropical forest hydrology research in North East Australia is a focal point for comparison with international activities elsewhere. The impacts of climate variability and change are considered briefly, as well as those of reforestation of degraded land on the land use hydrology, which requires a longer term vision and support of long term experimental catchments. Sadly, too few long term experimental catchments have been maintained in the humid tropics and there have been some significant closures even of these sites in recent years. Yet the case for long-term experiments is strengthened by the problematic issue of separating anthropogenic influences (such as land use change) on the hydrology of landscapes from the effects of climate variability at a time of escalation in population and related socio-economic pressures in the humid tropics. Particular emphasis is made of the need for greater consideration for the social and cultural dimensions of forest management within forest hydrology. Furthermore, scientists must be committed to incorporating ‘societal needs' in their planning of research projects, as well as in publicizing the applications of their results, within the framework of forest-land-water policy. Alarm is expressed at the extensive disregard for the application of existing forest hydrology ‘know how' in forest-land management manipulations associated with the humid tropics.

scholarly journals Iron oxides and aluminous clays selectively control soil carbon storage and stability in the humid tropics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maximilian Kirsten ◽  
Robert Mikutta ◽  
Cordula Vogel ◽  
Aaron Thompson ◽  
Carsten W. Mueller ◽  
...  
Keyword(s):  
Land Use ◽  
Weight Ratio ◽  
Terrestrial Ecosystems ◽  
Chemical Oxidation ◽  
Humid Tropics ◽  
Natural Forests ◽  
X Ray Diffraction ◽  
Microbial Decomposition ◽  
Threshold Range

AbstractClay minerals and pedogenic metal (oxyhydr)oxides are the most reactive soil mineral constituents controlling the long-term persistence of organic carbon (OC) in terrestrial ecosystems. However, their co-occurrence in most soils complicates direct assessment of their individual contribution to OC persistence. Making use of unique mineralogical combinations in soils located in the East Usambara Mountains of Tanzania, we disentangled the contribution of clay-sized aluminous minerals (kaolinite, gibbsite) and pedogenic Fe (oxyhydr)oxides (predominant goethite and hematite) on OC storage and stabilization under natural forests and croplands. Topsoil samples, varying in contents but not types of aluminous clays and pedogenic Fe (oxyhydr)oxides, were identified by selective extractions, X-ray diffraction, and Mössbauer spectroscopy. Associated abundance of particulate and mineral-associated organic matter (OM) was quantified by density fractionation and their changes during land-use conversion were determined as a measure of OC persistence. Additionally, we assessed the resistance of OC to chemical oxidation as well as microbial decomposition in a 50-day laboratory incubation. We found that the ratio of pedogenic Fe to aluminous clay is more consequential for OC storage and stabilization than their individual contents, despite the fact that Fe (oxyhydr)oxides generally exert a stronger impact on OC than aluminous clays. Conjunction of large amounts of Fe (oxyhydr)oxides with low aluminous clay contents caused the strongest accumulation of mineral-associated OC, a low soil respiration, high OC stability against chemical oxidation, and high OC persistence during land-use change. Our study suggests that certain mineralogical combinations in the humid tropics alleviate OM losses during land conversion because of the strong and selective mineral control on OC stabilization, particular if the weight ratio of pedogenic Fe to aluminous clay exceeds the threshold range of 0.44‒0.56.

scholarly journals Long-term trends in trunk diameter and tree height growth in planted forests in the humid tropics of West Java, Indonesia

Tropics ◽  
2007 ◽  
Vol 17 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Motoshi HIRATSUKA ◽  
Takeshi TOMA ◽  
Nina MINDAWATI ◽  
Ika HERIANSYAH ◽  
Yasushi MORIKAWA
Keyword(s):  
Tree Height ◽  
Height Growth ◽  
Humid Tropics ◽  
Planted Forests ◽  
West Java ◽  
Trunk Diameter ◽  
Long Term Trends ◽  
Tree Height Growth

scholarly journals The effect of biochar, lime and ash on maize yield in a long-term field trial in a Ultisol in the humid tropics

2020 ◽  
Vol 719 ◽  
pp. 137455 ◽  
Author(s):  
Sarah E. Hale ◽  
Neneng L. Nurida ◽  
Jubaedah ◽  
Jan Mulder ◽  
Erlend Sørmo ◽  
...  
Keyword(s):  
Field Trial ◽  
Maize Yield ◽  
Humid Tropics ◽  
Term Field

scholarly journals Afforestation by natural regeneration or by tree planting: examples of opposite hydrological impacts evidenced by long-term field monitoring in the humid tropics

2015 ◽  
Vol 12 (12) ◽  
pp. 12615-12648 ◽  
Author(s):  
G. Lacombe ◽  
O. Ribolzi ◽  
A. de Rouw ◽  
A. Pierret ◽  
K. Latsachak ◽  
...  
Keyword(s):  
Land Use ◽  
Natural Regeneration ◽  
Land Use Changes ◽  
Humid Tropics ◽  
Tree Planting ◽  
Trend Detection ◽  
Tree Plantations ◽  
Positive Effects ◽  
Term Field

Abstract. The humid tropics are exposed to an unprecedented modernization of agriculture involving rapid and highly-mixed land-use changes with contrasted environmental impacts. Afforestation is often mentioned as an unambiguous solution for restoring ecosystem services and enhancing biodiversity. One consequence of afforestation is the alteration of streamflow variability controlling habitats, water resources and flood risks. We demonstrate that afforestation by tree planting or by natural forest regeneration can induce opposite hydrological changes. An observatory including long-term field measurements of fine-scale land-use mosaics and of hydro-meteorological variables has been operating in several headwater catchments in tropical Southeast Asia since 2001. The GR2M water balance model repeatedly calibrated over successive 1 year periods, and used in simulation mode with specific rainfall input, allowed the hydrological effect of land-use change to be isolated from that of rainfall variability in two of these catchments in Laos and Vietnam. Visual inspection of hydrographs, correlation analyses and trend detection tests allowed causality between land-use changes and changes in seasonal flows to be ascertained. In Laos, the combination of shifting cultivation system (alternation of rice and fallow) and the gradual increase of teak tree plantations replacing fallow, led to intricate flow patterns: pluri-annual flow cycles induced by the shifting system, on top of a gradual flow increase over years caused by the spread of the plantation. In Vietnam, the abandonment of continuously cropped areas mixed with patches of tree plantations led to the natural re-growth of forest communities followed by a gradual drop in streamflow. Soil infiltrability controlled by surface crusting is the predominant process explaining why two modes of afforestation (natural regeneration or planting) led to opposite changes in flow regime. Given that commercial tree plantations will continue to expand in the humid tropics, careful consideration is needed before attributing to them positive effects on water and soil conservation.

scholarly journals Contradictory hydrological impacts of afforestation in the humid tropics evidenced by long-term field monitoring and simulation modelling

2016 ◽  
Vol 20 (7) ◽  
pp. 2691-2704 ◽  
Author(s):  
Guillaume Lacombe ◽  
Olivier Ribolzi ◽  
Anneke de Rouw ◽  
Alain Pierret ◽  
Keoudone Latsachak ◽  
...  
Keyword(s):  
Land Use ◽  
Rainfall Variability ◽  
Land Use Changes ◽  
Humid Tropics ◽  
Tree Planting ◽  
Trend Detection ◽  
Tree Plantations ◽  
Positive Effects ◽  
Term Field

Abstract. The humid tropics are exposed to an unprecedented modernisation of agriculture involving rapid and mixed land-use changes with contrasted environmental impacts. Afforestation is often mentioned as an unambiguous solution for restoring ecosystem services and enhancing biodiversity. One consequence of afforestation is the alteration of streamflow variability which controls habitats, water resources, and flood risks. We demonstrate that afforestation by tree planting or by natural forest regeneration can induce opposite hydrological changes. An observatory including long-term field measurements of fine-scale land-use mosaics and of hydrometeorological variables has been operating in several headwater catchments in tropical southeast Asia since 2000. The GR2M water balance model, repeatedly calibrated over successive 1-year periods and used in simulation mode with the same year of rainfall input, allowed the hydrological effect of land-use change to be isolated from that of rainfall variability in two of these catchments in Laos and Vietnam. Visual inspection of hydrographs, correlation analyses, and trend detection tests allowed causality between land-use changes and changes in seasonal streamflow to be ascertained. In Laos, the combination of shifting cultivation system (alternation of rice and fallow) and the gradual increase of teak tree plantations replacing fallow led to intricate streamflow patterns: pluri-annual streamflow cycles induced by the shifting system, on top of a gradual streamflow increase over years caused by the spread of the plantations. In Vietnam, the abandonment of continuously cropped areas combined with patches of mix-trees plantations led to the natural re-growth of forest communities followed by a gradual drop in streamflow. Soil infiltrability controlled by surface crusting is the predominant process explaining why two modes of afforestation (natural regeneration vs. planting) led to opposite changes in streamflow regime. Given that commercial tree plantations will continue to expand in the humid tropics, careful consideration is needed before attributing to them positive effects on water and soil conservation.

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