冀北坝上地区榆树和樟子松人工林降雨再分配特征研究

Study on rainfall redistribution characteristics of Ulmus pumila and Pinus sylvestris var.mongolica plantations in Bashang area,northern Hebei Province

为明确冀北坝上地区主要人工林降雨再分配特征,在河北省承德市丰宁满族自治县大滩镇以林分结构相似的榆树(Ulmus pumila)和樟子松(Pinus sylvestris var.mongolica)人工林为研究对象,测定每场降雨2种人工林林冠截留各水文分量,分析其降雨再分配特征及影响因素。结果表明:(1)榆树和樟子松人工林的林冠截留量与林外降雨量分别呈指数关系和对数关系。(2)郁闭度较小的情况下,2种人工林的林内降雨量与林外降雨量都呈线性关系。(3)榆树和樟子松人工林分别在林外降雨量为0.25 mm和4.58 mm时开始产生树干茎流,且与林外降雨量均呈线性关系;榆树树皮对树干茎流的阻拦和吸收作用大于樟子松。(4)2种人工林的林内降雨量均显著大于林冠截留量和树干茎流量;在降雨量较小时,林冠截留量显著大于树干茎流量,随着雨量级的增加,树干茎流量会超过林冠截留量。(5)风增大了榆树人工林的林内降雨量并减小了林冠截留量和树干茎流量,对樟子松人工林林冠截留各水文分量影响不大。综上所述,不同人工林对降雨再分配作用会受到降雨量、树干、林冠等特征和风的影响,樟子松人工林的林冠截留作用更为稳定。

To clarify the rainfall redistribution characteristics of major plantation forests in the Bashang area of northern Hebei Province,Ulmus pumila plantation and Pinus sylvestris var.mongolica plantation with similar stand structure were used as research objects in Datan Town,Fengning Manchu Autonomous County,Chengde City,Hebei Province,China,and their rainfall redistribution characteristics and influencing factors were analyzed by measuring each hydrological volume canopy interception of the two plantations for each rainfall event.The results showed that:(1)The canopy interception and rainfall outside the forest of elm plantations and camphor pine plantations showed exponential and logarithmic relationships,respectively.(2)The rainfall inside the forest and rainfall outside the forest of both plantations were linearly related under the condition of less canopy density.(3)U.pumila plantations and P.sylvestris var.mongolica plantation started to produce stem flow at 0.25 mm and 4.58 mm of rainfall outside the forest,respectively;The relationship between stem flow and out-forest rainfall was linear in both plantations.Moreover the elm bark had a greater effects of blocking and absorption on trunk stem flow than sphagnum pine.(4)The in-forest rainfall of both plantations were significantly greater than the cumulative canopy interception and stem flow.Moreover the canopy interception was significantly greater than the stem flow when the rainfall was small,and the stem flow would exceed the canopy interception as the rainfall level increased.(5)Wind increased the in-forest rainfall and reduced the canopy retention and stem flow in U.pumila plantations,but had little effect on each hydrological volume intercepted by the canopies of P.sylvestris var.mongolica plantation.In conclusion,the effect of rainfall redistribution in different plantations was influenced by the characteristics of rainfall,stem and canopy and wind,the canopy interception of P.sylvestris var.mongolica plantation was more stable.