蔷薇科经济林液流特征及环境因子对其的影响

Characteristics of Sap Flow in Rosaceae Economic Forest and Its Response to environmental factors

为探明北京市蔷薇科经济林树种液流特征,以4种蔷薇科树种为研究对象,利用热扩散探针式茎流仪连续测定各树种液流变化,结合同步监测的环境因子,探究环境因子对各树种液流的影响。结果表明:各蔷薇科树种液流变化具有明显昼夜差异,液流增强时间段为05:00—09:30,液流减弱时间段为17:30—23:00。晴天时各树种液流变化趋势呈单峰型或双峰型。各树种生长季内液流密度逐渐增加,在6、7月份达到峰值后缓慢减少,直至树种休眠期时液流密度趋近0。生长季内各树种耗水强度由大到小依次为:李树(5.64 cm^(3)·cm^(-2)·h^(-1))、杏树(5.03 cm^(3)·cm^(-2)·h^(-1))、梨树(3.26 cm^(3)·cm^(-2)·h^(-1))、桃树(2.43 cm^(3)·cm^(-2)·h^(-1))。各树种液流受到水汽压亏缺(V_(PD))、太阳辐射(R_(s))、降水量(P)、大气相对湿度(R_(H))、大气温度(T_(a))、土壤水势(S_(WP))等环境因子直接或间接影响,树干液流与V_(PD)、R_(s)、T_(a)、S_(WP)呈正相关,与R_(H)呈负相关。各树种液流对环境因子的响应始终保持相似性和时滞性,时滞程度受到天气、季节、物候等因素影响。树干液流变化虽受到多环境因子共同作用,但当某一环境因子的影响程度过大时,会打破各环境因子共同作用于液流的微妙平衡。杏树树种液流对环境因子响应程度最大为R_(s)、T_(a)、S_(WP),李树为R_(s),梨树为R_(s)、S_(WP),桃树为R_(s)、V_(PD)。

In order to find out the sap flow characteristics of economic forest tree species in Beijing,with six economic forest tree species,the thermal diffusion probe stem flow meter was used to continuously measure the sap flow changes of each tree species,combined with the environmental factors monitored synchronously,the response law of sap flow of various economic forest species to environmental factors was revealed.The changes of sap flow of various economic forest species have obvious differences between day and night.The time period of sap flow enhancement is 5:00-9:30,and the time period of sap flow weakening is 17:30-23:00.The change trend of sap flow of each tree species is roughly the same on sunny days,showing a“single peak”or“double peak”type.The sap flow density gradually increased during the growing season of each tree species,reached a peak in June and July,and then decreased slowly until the tree species dormancy period,and the sap flow activity approached zero,maintain the minimum range of individual survival;average sap flow density of various tree species in the growing season in descending order of Prunes salicina(5.64 cm^(3)·cm^(-2)·h^(-1)),Armeniaca vulgaris(5.03 cm^(3)·cm^(-2)·h^(-1)),Amygdalus persica(3.26 cm^(3)·cm^(-2)·h^(-1))and Pyrus spp(2.43 cm^(3)·cm^(-2)·h^(-1)).The sap flow of each tree species is directly or indirectly affected by environmental factors such as water vapor pressure deficit(V_(PD)),solar radiation(R_(s)),precipitation(P),atmospheric relative humidity(R_(H)),atmospheric relative temperature(T_(a)),and soil water potential(S_(WP)).Indirectly,the trunk sap flow was positively correlated with V_(PD),R_(s),T_(a)and S_(WP),and negatively correlated with R_(H).The response of sap flow of various tree species to environmental factors remains similar.Although the change of trunk sap flow is affected by multiple environmental factors;when the influence of a certain environmental factor is too large,it will break the balance of the various environmental factors acting together on the flow change,forming a“dominant”situation.The sap flow of each tree species has the largest response to each environmental factor:for Armeniaca vulgaristhe factorsare R_(s),T_(a)and S_(WP);for Prunes salicinathe factorsis R_(s);for Pyrus spp the factors are R_(s)and S_(WP);and for Amygdalus persica the factors are R_(s)and V_(PD).