Stream ecosystem integrity is impaired by logging and shifting agriculture in a global megadiversity center (Sarawak, Borneo)

Abstract

► We compare ecosystem integrity of pristine vs. logged vs. farmed streams in Borneo. ► We use both functional (leaf breakdown) and structural indicators (associated fauna). ► Both practices alter ecosystem integrity, but the impacts of logging are more severe. ► Mechanized logging affects both the structure and function of stream ecosystems. ► Slash and burn clearing for shifting agriculture affects structure more than function. Keywords: Ecological integrity Structural and functional indicators Decomposition Shredder assemblages Farming Logging a b s t r a c tIn common with most of Borneo, the Bakun region of Sarawak is currently subject to heavy deforestation mainly due to logging and, to a lesser extent, traditional slash-and-burn farming practices. This has the potential to affect stream ecosystems, which are integrators of environmental change in the surrounding terrestrial landscape. This study evaluated the effects of both types of deforestation by using functional and structural indicators (leaf litter decomposition rates and associated detritivores or 'shredders', respectively) to compare a fundamental ecosystem process, leaf litter decomposition, within logged, farmed and pristine streams. Slash-and-burn agricultural practices increased the overall rate of decomposition despite a decrease in shredder species richness (but not shredder abundance) due to increased microbial decomposition. In contrast, decomposition by microbes and invertebrates was slowed down in the logged streams, where shredders were less abundant and less species rich. This study suggests that shredder communities are less affected by traditional agricultural farming practices, while modern mechanized deforestation has an adverse effect on both shredder communities and leaf breakdown..

Urbanization affects food webs and leaf-litter decomposition in a tropical stream in Malaysia

“…Some tropical invertebrates clearly differ from temperate species in terms of pollution tolerance. For example, Ephemeroptera and Chironomidae in the region (Yule et al 2010, Jinggut et al 2012) seem to be more pollution tolerant than their temperate counterparts, in part because they are adapted to elevated temperatures, and are small with shorter life cycles (Marchant 1982, Schowalter 2006.…”

“…However, Del Arco et al (2012) reported that temperate urban streams in Portugal exhibited slower litter decomposition than forested streams. Jinggut et al (2012) reported a gradient of decomposition rates in Bornean streams flowing through undisturbed, farmed, and logged forests, and attributed slower decomposition rates to high rates of sedimentation in the logged stream and increased microbe-mediated decomposition consequent to external nutrient inputs from agricultural practices. Chadwick et al (2006) reported that high levels of toxic compounds can impede microbial activity and retard litter breakdown, but such conditions would be more likely to arise from industrial pollution or mining activities than the lower levels of pollutants in household and stormwater discharge in Ampang River.…”

Effects of litter diversity on decomposition and biological colonization of submerged litter in temperate and tropical streams

“…In many parts of the world, landuse change, particularly loss of riparian vegetation, has resulted in loss of diversity and major shifts in the structural and functional organization of macroinvertebrates in streams (Allan 2004, Benstead and Pringle 2004, Jinggut et al 2012). Loss of riparian forests increases stream temperatures through loss of shade (Baxter et al 2005), reduces inputs of leaf litter, and affects the relative differences between wet and dry seasons (Wantzen et al 2008).…”

La descomposición de la hojarasca como herramienta para evaluar la integridad funcional de ríos altoandinos del sur del Ecuador

“…Mientras que un mayor grado de intervención de las zonas ribereñas en las microcuencas Llaviuco y Matadero pudo afectar significativamente estas comunidades, lo que no permitió diferenciar la actividad de los invertebrados y la de los microorganismos durante el proceso de descomposición. El cociente K g /K f ha sido utilizado para evaluar la importancia de los invertebradores fragmentadores en ríos tropicales (Jinggut, Yule, & Boyero, 2012;Masese et al, 2014;Casotti et al, 2015). De acuerdo a Boyero et al (2015) muchos sitios tropicales que tienen K g /K f >fragmentadores en la descomposición de la hojarasca es importante.…”