Abstract
Invertebrates are dominant species in primary tropical rainforests, where their abundance and diversity contributes to the functioning and resilience of these globally important ecosystems. However, more than one-third of tropical forests have been logged, with dramatic impacts on rainforest biodiversity that may disrupt key ecosystem processes. We find that the contribution of invertebrates to three ecosystem processes operating at three trophic levels (litter decomposition, seed predation and removal, and invertebrate predation) is reduced by up to one-half following logging. These changes are associated with decreased abundance of key functional groups of termites, ants, beetles and earthworms, and an increase in the abundance of small mammals, amphibians and insectivorous birds in logged relative to primary forest. Our results suggest that ecosystem processes themselves have considerable resilience to logging, but the consistent decline of invertebrate functional importance is indicative of a human-induced shift in how these ecological processes operate in tropical rainforests.
Highlights
Invertebrates are dominant species in primary tropical rainforests, where their abundance and diversity contributes to the functioning and resilience of these globally important ecosystems
We found a 15% decrease in the rate of leaf litter decomposition (likelihood ratio test, w2(1) 1⁄4 5.90, P 1⁄4 0.015, N 1⁄4 25) in logged compared with primary forest, a 13% increase in the rate at which seeds were removed and/or predated (likelihood ratio test, w2(1) 1⁄4 3.98, P 1⁄4 0.047, N 1⁄4 194), and no difference in invertebrate predation rate (Fig. 1; likelihood ratio test, w2(1) 1⁄4 1.03, P 1⁄4 0.310, N 1⁄4 51; Supplementary Table 1)
Experimental manipulations demonstrated that invertebrates contributed significantly less to delivering all three ecosystem processes in logged relative to primary forest (Fig. 1)
Summary
Invertebrates are dominant species in primary tropical rainforests, where their abundance and diversity contributes to the functioning and resilience of these globally important ecosystems. We find that the contribution of invertebrates to three ecosystem processes operating at three trophic levels (litter decomposition, seed predation and removal, and invertebrate predation) is reduced by up to one-half following logging. These changes are associated with decreased abundance of key functional groups of termites, ants, beetles and earthworms, and an increase in the abundance of small mammals, amphibians and insectivorous birds in logged relative to primary forest. Our results are consistent with those expected in a resilient ecosystem, with that resilience conferred through functional similarity between invertebrates and vertebrates
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