Search

Tropical forest management is a quintessential interdisciplinary (ID) problem straddling the social-natural divide, and has attracted scholars from many disciplines. This paper is a review of the ID research on tropical forests with a view to understanding the challenges involved in doing ID environmental research in general and the manner in which they might be addressed. Research on two core interdisciplinary questions in tropical forest research, namely causes of tropical forest loss and degradation and its impacts on society, is analysed to illuminate issues facing ID researchers. The challenges stem from differences in implicit values, theories and epistemologies across disciplines, as well as the relationship between individual disciplines, the ID space and the wider applied research audience. Understanding the value-laden nature of terms such as forest loss and degradation leads to a multidimensional and multidisciplinary characterization of the impact of forest change on human well-being. The analysis of causes of change has been enriched by ID research in which forest outcomes are characterized explicitly in terms of their values, measured in terms relevant to these values and linked to chains of socioeconomic variables at the appropriate scale. Explanations from different disciplines may be reconciled to some extent by seeing each as partial and perhaps having context-specific validity, although some core tensions, especially between economists and anthropologists, remain. Insights from ID research have been unevenly internalized in the literature, pointing to the absence of a broadly shared ID space as a consequence of individual social science disciplines appropriating environment as a subject of study. Shifting from theory-driven to problem-driven research and re-engaging self-consciously in this applied ID space will be required to generate more rigorous and relevant ID research on forests. [ABSTRACT FROM PUBLISHER]

Summary: The effects of forest degradation and use and establishment of tree-plantations on degraded or modified forest ecosystems at multi-decadal time-scales using tree-plantations on the streamflow response are less studied in the humid tropics when compared to deforestation and forest conversion to agriculture. In the Western Ghats of India (Uttar Kannada, Karnataka State), a previous soil hydraulic conductivity survey linked with rain IDF (intensity–duration–frequency) had suggested a greater occurrence of infiltration-excess overland within the degraded forest and reforested areas and thus potentially higher streamflow (Bonell et al., 2010). We further tested these predictions in Uttar Kannada by establishing experimental basins ranging from 7 to 23ha across three ecosystems, (1) remnant tropical evergreen Forest (NF), (2) heavily-used former evergreen forest which now has been converted to tree savanna, known as degraded forest (DF) and (3) exotic Acacia plantations (AC, Acacia auriculiformis) on degraded former forest land. In total, 11 basins were instrumented (3 NF, 4 AC and 4 DF) in two geomorphological zones, i.e., Coastal and Up-Ghat (Malnaad) and at three sites (one Coastal, two Up-Ghat). The rainfall–streamflow observations collected (at daily and also at a 36min time resolutions in the Coastal basins) over a 2–3year period (2003–2005) were analysed. In both the Coastal and Up-Ghat basins, the double mass curves showed during the rainy season a consistent trend in favour of more proportion of streamflow in the rank order DF>AC>NF. These double mass curves provide strong evidence that overland flow is progressively becomes a more dominant stormflow pathway. Across all sites, NF converted 28.4±6.41stdev% of rainfall into total streamflow in comparison to 32.7±6.97stdev% in AC and 45.3±9.61stdev% in DF. Further support for the above trends emerges from the quickflow ratio QF /Q for the Coastal basins. There are much higher values for both the DF and AC land covers, and their rank order DF>AC>NF. The quickflow response ratio QF /P is also the highest for the DF basin, and along with the QF /Q ratio, can exceed 90%. The corresponding delayed flow response ratios, QD /P clearly show the largest QD yields as a proportion of event precipitation from the Forest (NF1). The application of linear model supported these differences (e.g. 10–36% difference between NF and DF, p <0.001) in the storm hydrologic response of the Coastal basins. The exception was QF /P where there was a higher uncertainty connected with inter-basin mean differences. Cross-correlation plots for rain–streamflow and corresponding lag regression models for three storm events in the Coastal basins suggested the existence of alternative stormflow pathways with multiple lags with peaks between ∼12 and 24h in NF, compared to respective bimodal peaks at ∼1 and 16h in AC and ∼1 and 12h in DF. The long time lags for NF are suggestive of deep subsurface stormflow and groundwater as the contributing sources to the storm hydrograph. The short time lags in DF and AC are indicative of overland flow and so ‘memory’ of the previous degraded land cover is retained in AC as supported by previous hydraulic conductivity data. As potential and actual evapotranspiration is likely to be depressed during the monsoon, differences in streamflow and run-off responses between land-cover types is largely attributed to differences in soil infiltration and hydrologic pathways. Enhancing infiltration and reducing run-off in managed ecosystems should be explored in the terms of the context of other ecosystem services and biodiversity. [Copyright &y& Elsevier]