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Huang W.,Nanjing Forestry University | McDowell W.H.,University of New Hampshire | Zou X.,Nanjing Forestry University | Zou X.,University of Puerto Rico at San Juan | And 4 more authors.
PLoS ONE | Year: 2013

Stream water dissolved organic carbon (DOC) correlates positively with soil organic carbon (SOC) in many biomes. Does this relationship hold in a small geographic region when variations of temperature, precipitation and vegetation are driven by a significant altitudinal gradient? We examined the spatial connectivity between concentrations of DOC in headwater stream and contents of riparian SOC and water-soluble soil organic carbon (WSOC), riparian soil C:N ratio, and temperature in four vegetation types along an altitudinal gradient in the Wuyi Mountains, China. Our analyses showed that annual mean concentrations of headwater stream DOC were lower in alpine meadow (AM) than in subtropical evergreen broadleaf forest (EBF), coniferous forest (CF), and subalpine dwarf forest (SDF). Headwater stream DOC concentrations were negatively correlated with riparian SOC as well as WSOC contents, and were unrelated to riparian soil C:N ratio. Our findings suggest that DOC concentrations in headwater streams are affected by different factors at regional and local scales. The dilution effect of higher precipitation and adsorption of soil DOC to higher soil clay plus silt content at higher elevation may play an important role in causing lower DOC concentrations in AM stream of the Wuyi Mountains. Our results suggest that upscaling and downscaling of the drivers of DOC export from forested watersheds when exploring the response of carbon flux to climatic change or other drivers must done with caution. © 2013 Huang et al.

Li L.,Nanjing Forestry University | Li L.,University of Florida | Vogel J.,Texas A&M University | He Z.,University of Florida | And 6 more authors.
PLoS ONE | Year: 2016

Forest soils play a critical role in the sequestration of atmospheric CO2 and subsequent attenuation of global warming. The nature and properties of organic matter in soils have an influence on the sequestration of carbon. In this study, soils were collected from representative forestlands, including a subtropical evergreen broad-leaved forest (EBF), a coniferous forest (CF), a subalpine dwarf forest (DF), and alpine meadow (AM) along an elevation gradient on Wuyi Mountain, which is located in a subtropical area of southeastern China. These soil samples were analyzed in the laboratory to examine the distribution and speciation of organic carbon (OC) within different size fractions of water-stable soil aggregates, and subsequently to determine effects on carbon sequestration. Soil aggregation rate increased with increasing elevation. Soil aggregation rate, rather than soil temperature, moisture or clay content, showed the strongest correlation with OC in bulk soil, indicating soil structure was the critical factor in carbon sequestration of Wuyi Mountain. The content of coarse particulate organic matter fraction, rather than the silt and clay particles, represented OC stock in bulk soil and different soil aggregate fractions. With increasing soil aggregation rate, more carbon was accumulated within the macroaggregates, particularly within the coarse particulate organic matter fraction (250-2000 μm), rather than within the microaggregates (53-250μm) or silt and clay particles (< 53μm). In consideration of the high instability of macroaggregates and the liability of SOC within them, further research is needed to verify whether highly-aggregated soils at higher altitudes are more likely to lose SOC under warmer conditions. © 2016 Li et al.

Wang G.,Nanjing Forestry University | Zhou Y.,Nanning Landscape Administration Bureau | Xu X.,University of Oklahoma | Ruan H.,Nanjing Forestry University | Wang J.,Administrative Bureau of Wuyishan National Nature Reserve
PLoS ONE | Year: 2013

Soil organic carbon (SOC) actively participates in the global carbon (C) cycle. Despite much research, however, our understanding of the temperature sensitivity of soil organic carbon (SOC) mineralization is still very limited. To investigate the responses of SOC mineralization to temperature, we sampled surface soils (0-10 cm) from evergreen broad-leaf forest (EBF), coniferous forest (CF), sub-alpine dwarf forest (SDF), and alpine meadow (AM) along an elevational gradient in the Wuyi Mountains, China. The soil samples were incubated at 5, 15, 25, and 35°C with constant soil moisture for 360 days. The temperature sensitivity of SOC mineralization (Q10) was calculated by comparing the time needed to mineralize the same amount of C at any two adjacent incubation temperatures. Results showed that the rates of SOC mineralization and the cumulative SOC mineralized during the entire incubation significantly increased with increasing incubation temperatures across the four sites. With the increasing extent of SOC being mineralized (increasing incubation time), the Q10 values increased. Moreover, we found that both the elevational gradient and incubation temperature intervals significantly impacted Q10 values. Q10 values of the labile and recalcitrant organic C linearly increased with elevation. For the 5-15, 15-25, and 25-35°C intervals, surprisingly, the overall Q10 values for the labile C did not decrease as the recalcitrant C did. Generally, our results suggest that subtropical forest soils may release more carbon than expected in a warmer climate. © 2013 Wang et al.

Xu X.,Nanjing Forestry University | Xu X.,University of Oklahoma | Zhou Y.,Nanjing Forestry University | Ruan H.,Nanjing Forestry University | And 2 more authors.
Soil Biology and Biochemistry | Year: 2010

No consensus exists regarding soil organic carbon (SOC) lability and the temperature sensitivity of its decomposition. This lack of clear understanding limits the accuracy in predicting the long-term impacts of climate change on soil carbon (C) storage. In this study, we determined the temperature responses of labile and recalcitrant organic carbon (LOC vs. ROC) by comparing the time required to decompose a given amount of C at different incubation temperatures along an elevational gradient in the Wuyi Mountains in southeastern China. Results showed that the temperature sensitivity increased with increasing SOC recalcitrance (Q10-labile = 1.39 ± 0.04 vs. Q10-recalcitrant = 3.94 ± 0.30). Q10-labile and Q10-recalcitrant values significantly increased with increasing soil depth. The effect of elevational vegetation change was significant for Q10-recalcitrant but not for Q10-labile, though they increased along the elevational gradient. The response of ROC pools to changes in temperature would accelerate the soil-stored C losses in the Wuyi Mountains. Kinetic theory suggested that SOC decomposition was both temperature- and quality-dependent due to an increased temperature. This would promote more CO2 release from recalcitrant soil organic matter (SOM) in cold regions, resulting in a greater positive feedback to global climate change than previously expected. Moreover, the response of ROC to changes in temperature will determine the magnitude of the positive feedback due to its large storage in soils. © 2010.

Huang W.,Nanjing Forestry University | McDowell W.H.,University of New Hampshire | Zou X.,Nanjing Forestry University | Zou X.,University of Puerto Rico at San Juan | And 3 more authors.
Applied Geochemistry | Year: 2015

Terrestrial organic matter plays an important role in determining the chemical composition of headwater stream dissolved organic matter (DOM). We used excitation-emission matrix fluorescence spectroscopy (EEMs) and parallel factor analysis (PARAFAC) to detect the chemical composition of headwater stream DOM and riparian water-extractable soil organic matter (WSOM) among four different vegetation types, including evergreen broadleaf forest (EBF), coniferous forest (CF), subalpine dwarf forest (SDF) and alpine meadow (AM), along an altitudinal gradient (690-2060. m above sea level) in the Wuyi Mountains of subtropical China. Fluorescence index (FI) and biological/autochthonous index (BIX) values indicated that stream DOM was from terrestrial sources. Despite this link to terrestrial sources, the composition of stream DOM differed remarkably from that of riparian WSOM. Humic-like PARAFAC component C2 was observed in headwater streams, but not in riparian WSOM. Conversely, humic-like C3 compound was identified in riparian WSOM, but not in headwater streams. The relative abundance of humic-like C1 and C2 compounds did not differ among the headwater streams under four different vegetation types across the altitudinal gradient. In contrast, the relative abundance of C1 compounds in riparian WSOM was substantially higher in EBF than in other vegetation types. The relative abundance of tryptophan-like C4 compounds decreased from 26.47-54.26% in riparian WSOM to 5.71-14.24% in headwater streams. The relative abundance of tryptophan-like C4 compounds was higher in AM and EBF streams than in SDF and CF streams, and decreased in the order of AM. >. CF. >. SDF. >. EBF in the riparian WSOM. Our data suggest that variation in chemical composition of WSOM among four different vegetation types along an altitudinal gradient in the Wuyi Mountains does not induce corresponding changes in the chemical composition of stream DOM. Biogeochemical processes of plant-litter input directly into streams and bio-degradation and selective adsorption of DOM along a generalized hydrologic flow path from soil to stream may cause these qualitative differences between stream DOM and riparian WSOM composition across four different vegetation types along an altitudinal gradient in the Wuyi Mountains. © 2014 Elsevier Ltd.

Guo L.-J.,Shangrao Normal University | Li M.,Shangrao Normal University | Lin S.,Administrative Bureau of Wuyishan National Nature Reserve
Forest Research | Year: 2015

The flowering phenology, reproductive module and the relationship between the parameters and their impacting factors of Emmenopterys henryi were studied using field survey method. The results showed that the E. henryi trees entered the reproductive period at the age of 23 years old, and its florescence of single flower was 6.91 days. With the tree got old, its florescence came earlier, with a time duration of 36 to 61 days. Altitude had a significant influence on the florescence of single flower, as the altitude increased, the florescence of single flower got longer, and the first-flowering date postponed. The average number of flower branch per individual was 86, which including 7388 flowers and 95 fruits, and as the mother tree got old, the quantity of the reproductive module increased to different extends, among which the highest fruit productivity of a single flower branch generated from the trees with the age of 80~110 years old. With the altitude increased, both the number of flower branch and flower decreased, however the quantity of the fruits had a modest increase. There were significant positive correlations between the age of E. henryi and light, air temperature, air humidity and their modules. The results of the study indicated that, for the mother trees with age of 80~110 years old, the microhabitat of light intensity of 30000 lux, temperature of 28℃, and the humidity of 70%, were the best for their sexual reproduction. Based on the present research, it is suggested that the original habitat of E. henryi should be protected, cutting the mother tree of E. henryi should be prohibited, meanwhile, the high trees around the E. henryi tree should be thinned to improve the light conditions and help the growth and development of E. henryi. © 2015, Chinese Academy of Forestry. All right reserved.

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