The effects of catchment and riparian forest quality on stream environmental conditions across a tropical rainforest and oil palm landscape in Malaysian Borneo

Freshwaters provide valuable habitat and important ecosystem services, but are threatened worldwide by habitat loss and degradation. In Southeast Asia, rainforest streams are particularly threatened by logging and conversion to oil palm, but we lack information on the impacts of this on freshwater environmental conditions, and the relative importance of catchment versus riparian-scale disturbance. We studied sixteen streams in Sabah, Borneo, including old growth forest, logged forest, and oil palm sites. We assessed forest quality in riparian zones and across the whole catchment, and compared it with stream environmental conditions including water quality, structural complexity and organic inputs. We found that streams with the highest riparian forest quality were nearly 4 °C cooler, over 20 cm deeper, had over 40% less sand, greater canopy cover, more stored leaf litter and wider channels than oil palm streams with the lowest riparian forest quality. Other variables were significantly related to catchment-scale forest quality, with streams in the highest quality forest catchments having 40% more bedrock and 20 times more dead wood, along with higher phosphorus, and lower nitrate-N levels compared to streams with the lowest catchment-scale forest quality. Although riparian buffer strips went some way to protecting waterways, they did not maintain fully forest-like stream conditions. In addition, logged forest streams still showed signs of disturbance 10-15 years after selective logging. Our results suggest that maintenance and restoration of buffer strips can help to protect healthy freshwater ecosystems, but logging practices and catchment-scale forest management also need to be considered.During this work SHL was funded by a Natural Environment Research Council (NERC) studentship (number 1122589), Proforest, the Varley Gradwell Travelling Fellowship, Tim Whitmore Fund, Panton Trust and the Cambridge University Commonwealth Fund. MP and RME were supported by European Research Council Project number 281986. HB was funded by the S.T. Lee Fund

Impacts of habitat fragmentation on genetic diversity in a tropical forest butterfly on Borneo

Many areas of rain forest now exist as habitat fragments, and understanding the impacts of fragmentation is important for determining the viability of populations within forest remnants. We investigated impacts of forest fragmentation on genetic diversity in the butterfly Mycalesis orseis (Satyrinae) in Sabah (Malaysian Borneo). We investigated mtDNA diversity in 90 individuals from ten forest sites typical of the sizes of forest remnants that currently exist in the region. Nucleotide diversity declined with increasing isolation of remnants, but there was no effect of remnant size or population size, and haplotype diversity was similar among sites. Thus, approximately 50 y after forest fragmentation, few changes in genetic diversity were apparent and remnants apparently supported genetically viable populations of this butterfly. Many studies have shown that responses of species to habitat fragmentation usually follow a time delay, and so we developed a Monte Carlo simulation model to investigate changes in genetic diversity over time in small remnants. Model output indicated a substantial time delay (> 100 y) between fragmentation and genetic erosion, suggesting that, in the smallest study remnants, an increased risk of extinction from reduced genetic diversity is likely in the longer term

Coefficient shifts in geographical ecology: an empirical evaluation of spatial and non-spatial regression

Copyright © 2009 The Authors. Copyright © ECOGRAPHY 2009.A major focus of geographical ecology and macro ecology is to understand the causes of spatially structured ecological patterns. However, achieving this understanding can be complicated when using multiple regressions, because the relative importance of explanatory variables, as measured by regression coefficients, can shift depending on whether spatially explicit or non-spatial modelling is used. However, the extent to which coefficients may shift and why shifts occur are unclear. Here, we analyze the relationship between environmental predictors and the geographical distribution of species richness, body size, range size and abundance in 97 multi-factorial data sets. Our goal was to compare standardized partial regression coefficients of non-spatial ordinary least squares regressions (i.e. models fitted using ordinary least squares without taking autocorrelation into account; “OLS models” hereafter) and eight spatial methods to evaluate the frequency of coefficient shifts and identify characteristics of data that might predict when shifts are likely. We generated three metrics of coefficient shifts and eight characteristics of the data sets as predictors of shifts. Typical of ecological data, spatial autocorrelation in the residuals of OLS models was found in most data sets. The spatial models varied in the extent to which they minimized residual spatial autocorrelation. Patterns of coefficient shifts also varied among methods and datasets, although the magnitudes of shifts tended to be small in all cases. We were unable to identify strong predictors of shifts, including the levels of autocorrelation in either explanatory variables or model residuals. Thus, changes in coefficients between spatial and non-spatial methods depend on the method used and are largely idiosyncratic, making it difficult to predict when or why shifts occur. We conclude that the ecological importance of regression coefficients cannot be evaluated with confidence irrespective of whether spatially explicit modelling is used or not. Researchers may have little choice but to be more explicit about the uncertainty of models and more cautious in their interpretation

Biodiversity of leaf-litter ants in fragmented tropical rainforests of Borneo: the value of publically and privately managed forest fragments

In view of the rapid rate of expansion of agriculture in tropical regions, attention has focused on the potential for privately-managed rainforest patches within agricultural land to contribute to biodiversity conservation. However, these sites generally differ in their history of forest disturbance and management compared with other forest fragments, and more information is required on the biodiversity value of these privately-managed sites, particularly in oil-palm dominated landscapes of SE Asia. Here we address this issue, using tropical leaf-litter ants in rainforest fragments surrounded by mature oil palm plantations in Sabah, Borneo as a model system. We compare the species richness and composition of ant assemblages in privately-managed forest fragments ('high conservation value' fragments; HCVs) with those in publically-managed fragments of forest (virgin jungle reserves; VJRs) and control sites in extensive tracts of primary forest. In this way, we test the hypothesis that privately-managed and publically-managed forest fragments differ in their species richness and composition as a result of differences in history and management and hence in habitat quality. In support of this hypothesis, we found that HCVs had much poorer habitat quality than VJRs, including lower sizes and densities of trees, less canopy cover, fewer dipterocarp trees and shallower leaf litter. Consequently, HCVs supported only half the species richness of ants in VJRs, which in turn supported 70 % of the species richness of control sites, with vegetation structure and composition explaining 77 % of the variation among forest fragments in ant species richness. HCVs were also much smaller than VJRs but there was only a weak relationship between fragment size and habitat quality, and species richness was not related to fragment size. VJRs supported 78 % of the 156 species found in extensive tracts of forest whereas HCVs supported only 22 %, which was only slightly higher than the proportion previously recorded in oil palm (19 %). These data support previous findings that publically-managed VJR fragments can make an important contribution to biodiversity conservation within agricultural landscapes. However, we suggest that for these HCVs to be effective as reservoirs of biodiversity, management is required to restore vegetation structure and habitat quality, for instance through enrichment planting with native tree species. © 2014 Springer Science+Business Media Dordrecht

Impacts of logging and rehabilitation on invertebrate communities in tropical rainforests of northern Borneo

The inclusion of carbon stock enhancements under the REDD+ framework is likely to drive a rapid increase in biosequestration projects that seek to remove carbon from the atmosphere through rehabilitation of degraded rainforests. Concern has recently been expressed, however, that management interventions to increase carbon stocks may conflict with biodiversity conservation. Focusing on a large-scale rainforest rehabilitation project in northern Borneo, we examine the broad impacts of selective logging and subsequent carbon enhancement across a wide range of invertebrate fauna by comparing the abundance of 28 higher-level taxa within two separate rainforest strata (leaf-litter and understorey) across unlogged, naturally-regenerating and rehabilitated forest. We additionally assess changes in functional composition by examining responses of different feeding guilds. Responses of individual taxa to forest management were idiosyncratic but logging resulted in more than a 20% increase in total invertebrate abundance, with fewer than 20% of taxa in either stratum having significantly lower abundance in logged forest. Rehabilitation resulted in a marked reduction in abundance, particularly among leaf-litter detritivores, but overall, there were much smaller differences between unlogged and rehabilitated forest than between unlogged and naturally regenerating forest in both total invertebrate abundance and the abundances of different feeding guilds. This applied to both strata with the exception of understorey herbivores, which were more abundant in rehabilitated forest than elsewhere. These results support previous data for birds suggesting that carbon stock enhancement in these forests has only limited adverse effects on biodiversity, but with some impacts on abundance within particular guilds

Assessing trophic position from nitrogen isotope ratios: effective calibration against spatially varying baselines

Nitrogen isotope signatures (δ¹⁵N) provide powerful measures of the trophic positions of individuals, populations and communities. Obtaining reliable consumer δ¹⁵N values depends upon controlling for spatial variation in plant δ¹⁵N values, which form the trophic 'baseline'. However, recent studies make differing assumptions about the scale over which plant δ¹⁵N values vary, and approaches to baseline control differ markedly. We examined spatial variation in the δ¹⁵N values of plants and ants sampled from eight 150-m transects in both unlogged and logged rainforests. We then investigated whether ant δ¹⁵N values were related to variation in plant δ¹⁵N values following baseline correction of ant values at two spatial scales: (1) using 'local' means of plants collected from the same transect and (2) using 'global' means of plants collected from all transects within each forest type. Plant δ¹⁵N baselines varied by the equivalent of one trophic level within each forest type. Correcting ant δ¹⁵N values using global plant means resulted in consumer values that were strongly positively related to the transect baseline, whereas local corrections yielded reliable estimates of consumer trophic positions that were largely independent of transect baselines. These results were consistent at the community level and when three trophically distinct ant subfamilies and eight abundant ant species were considered separately. Our results suggest that assuming baselines do not vary can produce misleading estimates of consumer trophic positions. We therefore emphasise the importance of clearly defining and applying baseline corrections at a scale that accounts for spatial variation in plant δ¹⁵N values

Trophic position of species commonly sampled in unlogged and logged forest.

<p>Mean trophic position±S.E. are shown for all species sampled at least 10 times in both types of forest. p values are: *≤0.05, **≤0.01, ***≤0.001. From left to right, species are: <i>Lophomyrmex bedoti, Hypoponera</i> sp1, <i>Ponera</i> sp4, <i>Anochetus graeffei, Pachycondyla</i> sp3, <i>Pheidole rabo, Tetramorium</i> sp2, <i>Oligomyrmex</i> sp1, <i>Hypoponera</i> sp7, <i>Pheidole tjibodana, Paratrechina</i> sp2, <i>Strumigenys</i> sp1, <i>Strumigenys fuarda, Eurhopalothrix jennya</i>.</p