【作者】 任军；

【导师】 徐程扬；

【作者基本信息】 北京林业大学 ， 森林培育学， 2009， 博士

【摘要】 林木根系呼吸作为森林土壤呼吸的重要组成部分,每年所消耗的呼吸底物总量占林木总光合作用产物的50%左右,是森林生态系统碳素循环主要途径之一,其变化动态将成为森林乃至整个陆地生态系统碳平衡重要影响因子。在森林生态系统中,林木自身要消耗40%～70%的净光合产物才能维持细根的周转,地下部分的净初级生产占总净初级生产的50%～80%,因此,根系呼吸对森林生产力有重要影响。本文以长白山阔叶红松林重要组成树种——水曲柳（Fraxinus mandshurica）为研究对象,以野外测试和室内分析相结合的研究方法,从不同径级根系呼吸特点及其对土壤氮素供给的反应入手,系统地研究了自然条件下不同林龄大树和人工栽培条件下苗木根系呼吸及其影响因素,对水曲柳根系呼吸、不同径级根系功能、物质分配及影响根系呼吸的环境因素和生理生态因素进行了探讨,并分析了根系内氮、碳代谢对根系呼吸的调控机理。本文主要有以下几个方面的研究结论:（1）长白山阔叶红松林内不同龄级水曲柳根系呼吸速率的季节变化动态比较明显（P＜0.01）,林木生长季节内根系呼吸呈“单峰”曲线;水曲柳根系比根呼吸速率随着树龄的增加而降低,而单位表面积呼吸速率则相反;不同径级根系呼吸速率在7月份或8月份达到最高值而在冬季最低;单位表面积根系呼吸速率随着根系直径的增加而提高,而比根呼吸速率则随根系直径的增加而降低;随着径级的增加根系维持呼吸所占比例逐渐提高,而生长呼吸则降低。自然条件下,水曲柳不同径级根系呼吸速率随着根系氮含量的提高而呈上升,但相关性随根系加粗而减小;不同树龄间水曲柳根系呼吸速率与根系氮含量的相关性没有显著变化。（2）自然条件下,不同林龄水曲柳各径级根系呼吸速率与空气温度、不同层次土壤温度均为显著的指数相关,而根系呼吸速率与土壤温度相关性随土壤层次的加深而下降;成熟林根系呼吸的Q₁₀值比幼林略高,表明高龄林木根系呼吸对土壤温度升高的反应比低龄林木敏感;自然条件下,水曲柳不同径级根系呼吸温度系数Q₁₀值在2.21～2.33之间变化,并与水曲柳根系径级呈负相关,表明水曲柳天然林中土壤温度变化对细根呼吸速率影响更大。当土壤湿度在一定阈值以下时,根系呼吸速率随土壤湿度增大而升高,而超过这一阈值根系呼吸速率则降低。水曲柳呼吸速率与土壤氮含量呈显著的线性正相关,其相关性随树木年龄的增加而减小,而随根系加粗而变大。（3）栽培条件下,水曲柳苗木根系呼吸速率具有明显的季节性变化,在生长季节其变化曲线为“单峰”型,7月最高,8月以后迅速下降,到10月下旬苗木停止生长时仅为维持呼吸。氮素浓度和氮素形态比例处理对水曲柳苗木根系呼吸季节动态的影响均达到显著水平,对Q₁₀值也有不同程度的影响。水曲柳苗木根系呼吸的Q₁₀值在2.37～4.64之间,并随根系径级加大而降低,说明水曲柳苗木细根呼吸对土壤温度变化的反应更为敏感。（4）水曲柳苗木根系呼吸速率与根系全氮含量呈线性相关,并在不同月份、不同根系径级间达到显著相关,而相关性随根系加粗而降低,根组织氮素浓度是影响根系呼吸作用的重要因素。根系呼吸速率与根系硝态氮含量和铵态氮含量也都呈显著线性正相关,并且呼吸速率与硝态氮含量的R²值明显高于其与铵态氮含量的R²值。根系呼吸速率与根系可溶性蛋白含量为显著对数相关,而与氮代谢关键酶NR和GS活性均呈显著线性正相关,并且根系呼吸速率与NR活性的相关性高于GS活性。水曲柳苗木不同径级根系呼吸速率与根系TNC（包括可溶性糖和淀粉）浓度呈显著的二项式关系。水曲柳苗木细根呼吸速率与根系总吸收面积和活跃吸收面积均呈显著的线性相关,并且根系单位表面积呼吸速率与根系活力相关性高于比根呼吸速率。更多还原

【Abstract】 As an important part of forest soil respiration,total respiratory substrate that tree root respiration consumed around 50%of trees total products of photosynthesis in every year,and tree root respiration were the main ways of the forest ecosystem carbon cycle,in addition it’s changes would be an important factor influencing the carbon balance of the whole land-ecosystem.In forest ecosystems,trees can maintain fine roots turnover while 40%～70%of the net photosynthesis product were consumed by trees itself.The net primary productions of underground part were 50%～80%of total net primary production. Therefore,the root respiration had important influence on the forest productivity.For exploring root respiration and its influencing factor,root function of different diameter of Fraxinus mandshurica,and analyzing regulation mechanism to root respiration about carbon and nitrogen metabolism,this paper systematically reaserch root respiration ofE mandshurica of the mixed forests of Moutain Changbai at different condition through combining research methods of field testing and laboratory analysis and from root respiration characteristic at different diameter and response to nitrogen supply.This paper has the following several aspects of the research results:（1） The root respiration rate of F.mandshurica had more apparent seasonal dynamic at different age class in Korean Pine forest of the Changbai mountain（P＜0.01）,and the highest respiration rate observed in July and lowest rate in October.In trees growing season,root respiration was a single peak curve affected by temperature,and specific root respiration rate was decreased with increasing trees age but superficial area respiration rate had a reverse trend.Among different diameter,specific root respiration rate decreased with increasing root diameter but superficial area respiration rate had a reverse trend.The proportions of root maintain respiration was gradually improved with increasing root diameter and the proportion of root growth respiration was depressed.In natural conditions,root respiration rate of F.mandshurica was increased with increasing root N contents at different root diameter,but the relativity was decreased with increasing root diameter. Among different age,the relativity between root respiration and root N contents was inapparent.（2） In natural conditions,different diameter root respiration rate of F.mandshurica increased exponentially with air temperture and soil temperature of different depth,and the relativity between root respiration and soil temperature was decreased with deepening soil.The Q₁₀ of mature stand was higher than that of young stand;apparently root respiration of mature stand was more sensitive to temperature than young stand.In natural conditions,the Q₁₀ that temperature coefficient of root respiration from 2.21 to 2.33,and it was decreased with increasing root diameter,indicating that fine roots was more easily affected by soil temperature change than that of thick roots in wild wood of F.mandshurica.More soil water in a certain range would improve root respiration rate,but excessive water in soil would restrain root respiration rate.The root respiration rate increased linearly with soil N contents,the relativity was lower with increasing trees age,and was raise with increasing root diameter.（3） In cultivating conditions,seasonal variation regularities of root respiration rate of F.mandshurica seedling were consistent with air temperature,moreover highest respiration rate observed in July and lowest rate in October.During the growth season,specific root respiration rate ranged from 0.5732μmol·g^-1.s^-1（root＜2 mm in diameter） to 7.1861μmol·g^-1.s⁹-1)（root＜2 mm） and superficial area respiration rate were from 0.0132μmol·cm^-1.s^-1（root＜2 mm） to 0.6848μmol·cm^-1.s^-1（root＞5 mm）. Specific root respiration rate decreased with increasing root diameter but superficial area respiration rate had a reverse trend.Air temperature rising influenced the response of root respiration to nitrogen fertility,and the influence was significant level（p＜0.05） between June and August.Root respiration rate increased exponentially with soil temperature at 10 cm（R²=0.779-0.981）,with a Q10 of 2.37 to 4.64. Apparently,fine roots was more sensitive to temperature than thick roots.Nitrogen fertility influenced the Q10 of fine roots（p=0.0392＜p=0.05） but not that of thick roots（p＞0.05）,thereby indicating that Q10 of fine roots was more easily affected by soil nitrogen concentration change than that of thick roots.（4） Root respiration rate of F.mandshurica seedling increased linearly with root N contents,the relativity was lower with increasing root diameter;indicate that the N concents of root tissue were major factor to root respiration.Root respiration rate increased also linearly with root nitrate nitrogen and root ammonium nitrogen contents,and the R² value bewteen root respiration and nitrate nitrogen was apparently higher than that bewteen root respiration and ammonium nitrogen.Root respiration apparetly increased logarithmic with root soluble protein contents.Root respiration rate apparetly increased linearly with the activity of key enzyme about nitrogen metabolism（NR and GS）,and the relativity bewteen root respiration and the activity of NR was higher than that bewteen root respiration and the activity of GS.Root respiration rate increased binomial with root TNC（including soluble sugar and starch） contents.Root respiration rate apparetly increased linearly with root absorption area,and the relativity bewteen superficial area respiration rate and absorption area was higher than that of specific root respiration rate.更多还原