Despite continued studies on the ecology and physiology of strangling hemiepiphytes, there is little quantitative information about the variations in source‐water uptake by these species under different growth phases. In this study, the water acquisition patterns of a hemiepiphyte, Ficus tinctoria, is investigated in relation to growth phase (epiphytic, transitional and terrestrial) and season (foggy, hot‐dry and rainy). Stable isotope compositions of water in xylem, soil, canopy humus, fog and rainfall were sampled on seasonally distinct dates, and soil water content and leaf carbon isotope composition were measured in order to determine the proportion of different water sources. Results indicated that F. tinctoria displayed a high degree of plasticity in source‐water acquisition associated with the growth‐phase transition from purely canopy‐rooted epiphyte to transitional plant to terrestrial tree. During the foggy season and the hot‐dry season, epiphytes utilized a combination of recently received rainwater (82–89%) and fog water (11–18%) present in canopy humus soil, whereas terrestrial trees exclusively depended on shallow and deep terrestrial soil water and exhibited marked flexibility in depth of soil water uptake. Transitional‐phase plants relied predominantly on shallow soil water (79–86%) and extracted only a small fraction of canopy humus water (14–21%). During the rainy season, epiphytes relied almost exclusively on recent rainwater (96%) and had a negligible water uptake from fog, whereas trees extracted their water primarily from the shallow soil and less from the deep soil. Plants in transitional‐phase drew a considerable fraction of water from canopy humus soil. This plasticity of source‐water uptake to cope with radical changes in rooting environment is likely the key feature enabling hemiepiphytic species to thrive and successfully establish in the tropical rainforests. Copyright © 2014 John Wiley & Sons, Ltd.

The Xishuangbanna (SW China) landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations. This study characterized the influence of conversion of tropical rainforest to rubber plantation on potential splash erosion rate and actual splash erosion rate. The average potential splash erosion rate was 2.1 times higher in the rubber plantation than in the open, while for the rainforest it was only 1.2 times higher than in the open, suggesting that the rubber plantation canopy greatly increased the rainsplash erosion. The average actual splash erosion rate was 2.0 times higher in the rubber plantation than in the rainforest, demonstrating that the rainforest was more effective in controlling splash erosion. The actual splash erosion rate was considerably lower in the terrace bench than in the riser bank in the rubber plantation, indicating that the riser bank was more sensitive to raindrop splash. Hence, protection of terrace risers with productive vegetation or litter/mulch layer is of vital importance in this bench-terraced rubber plantation. These results clearly show that conversion of tropical rainforest to rubber plantation had a negative effect on controlling splash erosion.

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While impervious surface expands with global urbanization, understanding the quality and quantity changes of soil organic carbon (SOC) under impervious surfaces is essential to assess the impacts of urbanization on the SOC pool and cycling. By comparing soils under impervious surfaces with surface and subsurface soils from adjoining open areas, we present a systematic study on the SOC signature under impervious surfaces. SOC concentration barely changed when comparing soils under impervious surfaces with subsurface soil from the nearby open area; however, the depletion on SOC was 35−62% when it was compared with surface soils. Regardless of comparison with surface or subsurface soils, bulk-level 13 C NMR spectra and specific molecular biomarkers showed a depletion in carbohydrates and an increase in aromatics in SOC composition. Such an alteration was greater with coverage by concrete slabs than simulated home structures built on crawl spaces and was greater as the coverage duration of residential home structures increased. Long-term coverage of residential home structures suppressed microbial degradation and selectively increased the sequestration of plant suberin-and lignin-derived carbon, which would likely increase the residence time of SOC. This study highlights a possible impact of urbanization on the SOC signature and emphasizes that biogeochemical impacts on SOC vary with the type of impervious surface and coverage time.

The thermal compensatory response of microbial respiration contributes to a decrease in warming-induced enhancement of soil respiration over time, which could weaken the positive feedback between the carbon cycle and climate warming. Climate warming is also predicted to cause a worldwide decrease in soil moisture, which has an effect on the microbial metabolism of soil carbon. However, whether and how changes in moisture affect the thermal compensatory response of microbial respiration are unexplored. Here, using soils from an 8-year warming experiment in an alpine grassland, we assayed the thermal response of microbial respiration rates at different soil moisture levels. The results showed that relatively low soil moisture suppressed the thermal compensatory response of microbial respiration, leading to an enhanced response to warming. A subsequent moisture incubation experiment involving offplot soils also showed that the response of microbial respiration to 100 d warming shifted from a slight compensatory response to an enhanced response with decreasing incubation moisture. Further analysis revealed that such respiration regulation by moisture was associated with shifts in enzymatic activities and carbon use efficiency.Our findings suggest that future drought induced by climate warming might weaken the thermal compensatory capacity of microbial respiration, with important consequences for carbon-climate feedback.