上海公园绿地常见乔木茎流特征及其影响因素

Characteristics and influencing factors of common tree stem flow in Shanghai park green spaces

公园绿地为上海城市提供了重要的生态系统服务,分析典型绿化树种茎流变化规律及其影响因素,探究蒸腾耗水特性,对进一步加强公园绿地维护和管理、提升生态功能具有重要意义。本研究以海湾国家森林公园2种常见乔木香樟(Camphora officinarum)与无患子(Sapindus saponaria)作为观测对象,采用插针式茎流计和自动气象站对树干茎流及周边气象因子开展连续监测,分析不同时间尺度下茎流速率与环境因子的相关关系。结果表明:香樟与无患子茎流均具有昼高夜低特征,香樟茎流速率日变化曲线呈现明显的“几”字形,无患子茎流速率日变化曲线则整体呈现“多峰”状态。与晴天相比,阴天和雨天条件下的香樟、无患子茎流启动、峰值、结束都有所抑制,具有迟起早退的特征。小时尺度下,香樟和无患子茎流速率均与光合有效辐射(Photosynthetically Active Radiation, PAR)、风速(Wind Speed, WS)、温度(Temperature, Ta)和土壤热通量(Soil Heat Flux, SG)呈现极显著正相关(p<0.01),相关性系数绝对值均大于0.65;与湿度(Humidness, RH)呈现极显著负相关(p<0.01),相关性系数分别为-0.89、-0.76。晴天香樟和无患子茎流速率与PAR、Ta、RH和SG具有极显著相关性(p<0.01);阴天香樟和无患子茎流速率除了受到与晴天有显著相关性的因子影响外,还与WS极显著正相关(p<0.01),相关性系数分别为0.84、0.62;受降雨影响,雨天香樟茎流速率与PAR、Ta、土壤体积含水量(Soil Volumetric Water Content, SVMC)、土壤温度(Soil Temperature, ST)和SG呈极显著正相关(p<0.01),土壤环境因子的影响作用凸显;雨天,除了WS外,无患子茎流速率与其他气象因子呈现与晴天和阴天相反的相关性,而受土壤因子的影响与晴天保持一致。研究结论可为区域公园绿地林地建设和管理提供参考。

The park green spaces in Shanghai provide vital ecosystem services for the city.Analyzing the stem flow change rule of typical green tree species and its influencing factors,as well as exploring the characteristics of transpiration water consumption,is of great significance for further strengthening the maintenance and management of park green space and improving ecological functions.This study focuses on two common arboreal species in the Haiwan National Forest Park,Camphora officinarum and Sapindus saponaria,as the subjects of observation.By employing needle-type stem flow meters and automatic weather stations,continuous monitoring of trunk stem flow and surrounding meteorological factors was conducted,and the correlation between stem flow rates and environmental factors was analyzed across different time scales.The results indicate that both Camphora officinarum and Sapindus saponaria exhibit diurnal patterns in stem flow,with higher rates during the day and lower at night.The daily variation curve of the stem flow rate of Camphora officinarum shows a distinct“several”shape,while that of Sapindus saponaria presents a“multi-peak”state overall.Compared to sunny days,the initiation,peak,and termination of stem flow in both species are suppressed under cloudy and rainy conditions,characterized by a late start and early end.On an hourly scale,the stem flow rates of both species show a highly significant positive correlation with photosynthetically active radiation(PAR),wind speed(WS),temperature(Ta),and soil heat flux(SG)(p<0.01),with correlation coefficients greater than 0.65 in absolute value;They also show a highly significant negative correlation with humidity(RH)(p<0.01),with correlation coefficients of-0.89 and-0.76,respectively.On sunny days,the stem flow rates of both species are highly significantly correlated with PAR,Ta,RH,and SG(p<0.01).On cloudy days,in addition to the factors significantly correlated with those on sunny days,the stem flow rates of both species are also highly significantly positively correlated with WS(p<0.01),with correlation coefficients of 0.84 and 0.62,respectively.Affected by rainfall,the stem flow rate of Camphora officinarum on rainy days is highly significantly positively correlated with PAR,Ta,soil volumetric water content(SVMC),soil temperature(ST),and SG(p<0.01),highlighting the prominent influence of soil environmental factors.On rainy days,except for WS,the stem flow rate of Sapindus saponaria shows opposite correlations with other meteorological factors compared to sunny and cloudy days,while the influence of soil factors remains consistent with that on sunny days.The conclusions of this study can provide valuable references for the construction and management of green land in regional parks.By understanding the stem flow variation patterns of different tree species under various environmental conditions,green space managers can formulate more scientific management measures such as irrigation,pruning,and pest control,thereby improving the ecological benefits and landscape effects of green spaces.Moreover,these findings can also guide the selection and configuration of urban greening tree species,further optimizing the urban green space system,enhancing the quality of the urban ecological environment,and providing citizens with healthier and more comfortable leisure spaces.