Structure and species composition of tree stands on verges and slopes along a major highway in Hong Kong

Arboricultural research focusing on transport land use was lacking in Hong Kong.Some highway slopes were registered in the Systematic Identification of Maintenance Responsibility of Slopes in the Territory(SIMAR),abbreviated as SIMAR slopes.We aimed to analyze patterns in the structure and species composition of the tree stock along a highway in Hong Kong and examined how a slope registration system could help explain the characteristics of urban forests.The 53 slopes and 52 verges along San Tin Highway,Hong Kong were randomly selected.The trees on each slope and verge were collectively sampled as a tree stand.Six variables,namely tree abundance,species richness,maximum tree height,Shannon-Wiener diversity,Simpson's dominance,and Pielou's evenness were measured for each stand.In addition,a limited visual tree risk assessment was performed.The 7,209 trees in 23 species were recorded.Species richness was low,ranging from one to eight species per stand.SIMAR and non-SIMAR slopes were compared.SIMAR slopes had significantly higher species richness,diversity,evenness but lower dominance,with mean difference of 1.41 species,0.17,0.17 and-0.28respectively.SIMAR slopes were associated with lower tree risk rating.When training regression models,boosting as an ensemble method arbitrarily raised the explanatory power and the predictive accuracy of some models.Slope height,length,angle and area could be significant predictors of the biodiversity-related variables.Future research can sample more habitat characteristics related to the structure and species composition of slopes and verges which were important components of urban forestry.

Source Range Estimation Based on Pulse Waveform Matching in a Slope Environment

An approach of source range estimation in an ocean environment with sloping bottom is presented. The approach is based on pulse waveform correlation matching between the received and simulated signals. An acoustic prop- agation experiment is carried out in a slope environment. The pulse signal is received by the vertical line array, and the depth structure can be obtained. For the experimental data, the depth structures of pulse waveforms are different, which depends on the source range. For a source with unknown range, the depth structure of pulse waveform can be first obtained from the experimental data. Next, the depth structures of pulse waveforms in dif- ferent ranges are numerically calculated. After the process of correlating the experimental and simulated signals, the range corresponding to the maximum value of the correlation coefficient is the estimated source range. For the explosive sources in the experiment with two depths, the mean relative errors of range estimation are both less than 7%.

Global and regional controls on carbon-sulfur isotope cycling during SPICE event in south China

The positive S-isotopic excursion of carbonate-associated sulfate(δ34S_(CAS))is generally in phase with the Steptoean positive carbon isotope excursion(SPICE),which may reflect widespread,global,transient increases in the burial of organic carbon and pyrite sulfate in sediments deposited under large-scale anoxic and sulphidic conditions.However,carbon-sulfur isotope cycling of the global SPICE event,which may be controlled by global and regional events,is still poorly understood,especially in south China.Therefore,theδ13CPDB,δ18OPDBδ34S_(CAS),total carbon(TC),total organic carbon(TOC)and total sulfate(TS)of Cambrian carbonate of Waergang section of Hunan Province were analyzed to unravel global and regional controls on carbon-sulfur cycling during SPICE event in south China.Theδ34S_(CAS)values in the onset and rising limb are not obviously higher than that in the preceding SPICE,meanwhile sulfate(δ34S_(CAS))isotope values increase slightly with increasingδ13CPDB in rising limb and near peak of SPICE(130–160 m).The sulfate(δ34S_(CAS))isotope values gradually decrease from 48.6‰to 18‰in the peak part of SPICE and even increase from 18%to 38.5%in the descending limb of SPICE.The abnormal asynchronous C−S isotope excursion during SPICE event in the south China was mainly controlled by the global events including sea level change and marine sulfate reduction,and it was also influenced by regional events such as enhanced siliciclastic provenance input(sulfate),weathering of a carbonate platform and sedimentary environment.Sedimentary environment and lithology are not the main reason for global SPICE event but influence theδ13CPDB excursion-amplitude of SPICE.Sea level eustacy and carbonate platform weathering probably made a major contribution to theδ13CPDB excursion during the SPICE,in particularly,near peak of SPICE.Besides,the trilobite extinctions,anoxia,organic-matter burial and siliciclastic provenance input also play an important role in the onset,early and late stage of SPICE event.