【作者】 刘波；

【导师】 徐小牛；

【作者基本信息】 安徽农业大学 ， 森林培育， 2008， 硕士

【摘要】 肖坑具有典型亚热带季风气候,其典型森林植被为亚热带常绿阔叶林。采用根钻土芯法和内生长法相结合的研究方法,系统研究了亚热带常绿阔叶林细根生物量的分布状况、不同年龄林分的细根生物量及季节动态变化、细根养分元素含量（N、P、K、Ca、Na、Mg、Fe）及其季节动态变化。采用切断根系法、运用Li-6400光合呼吸测定仪对不同年龄林分根系呼吸特性、及其对土壤呼吸的贡献和季节动态变化进行了研究,探讨了根系呼吸对土壤温度和含水量的响应。（1）常绿阔叶林细根生物量随土层的深度增加而逐渐减少,大部分细根集中于0～10 cm的土壤表层。中龄林细根生物量平均值为3.825 t·hm^-2,稍大于幼龄林(3.768 t·hm^-2)。在30 cm表土层内中龄林与幼龄林细根生物量季节波动性较大,都于6月达最高值。（2）常绿阔叶林30 cm土层内,中龄林细根年生长量为1.394 t·hm^-2·a^-1,与幼龄林细根年生长量(1.398 t·hm^-2·a^-1)非常接近。中龄林、幼龄林细根年周转率分布为0.36和0.37。细根生长量随季节变化明显:一年中,常绿阔叶林细根月均生长量范围为0.031～0.228 t·hm^-2·a^-1;月平均生长量最大值在3～6月,幼龄林可达到0.205 t·hm^-2·a^-1,而中龄林为0.228 t·hm^-2·a^-1。（3）中龄林与幼龄林细根中N、P、K、Ca、Mg、Na、Fe养分元素含量和细根生物量分布规律一致,垂直分布明显,随着土层深度的增加而减少,0～10 cm表土层细根养分含量最高。中龄林中各元素含量大小顺序为:Fe＞Ca＞N＞K＞Na＞Mg＞P:幼龄林为:Ca＞Fe＞K＞N＞Mg＞Na＞P。N、P、K、Na含量随季节变化不大。中龄林与幼龄林细根Ca含量一年中呈现“双峰”曲线波动:6月出现最大值,而11月又一次出现较高的峰值。Mg、Fe含量一年中均呈现“单峰”曲线变化,Mg含量最大值出现在9月,而最小值在1月:Fe含量最大值出现在6月,而最小值在11月。（4）中龄林与幼龄林细根的N、P、K、Ca、Na、Mg、Fe的养分现存量随着土层深度的增加而减少。0～10 cm土层细根养分现存量最高,特别是P元素,其现存量占30 cm表土层内细根该元素总量的70.81%,最低的是Na占48.42%。中龄林中,细根各养分元素的现存量大小为:Fe＞Ca＞N＞K＞Na＞Mg＞P;而幼龄林细根各养分元素的现存量大小为:Ca＞Fe＞K＞N＞Mg＞Na＞P,两种林分P现存量均为最少。中龄林细根N、P、K、Na、Fe的现存量大于幼龄林。细根养分现存量的变化与细根生物量和细根养分含量的变化有关。中龄林与幼龄林随季节动态变化基本一致。两林分细根N、P、Mg、Na的现存量随季节变化趋势不十分明显;Fe、Mg、Na的现存量呈“单峰”曲线变化,Fe最大值出现在6月,最小值出现在1月。Ca自4月开始增长较快,于6月达最大值,之后迅速下降,在9月达较低水平。Mg、Na于6月出现变化幅度较小的峰值。两林分中,K呈“双峰”曲线变化,峰值出现在6月和11月,最小值在9月。两林分细根P现存量周年处于较低水平,且季节变化极不明显。中龄林细根的N现存量显著高于幼龄林。（5）中龄林根系呼吸速率年变化范围在0.412～1.970μmol·m^-2·s^-1,幼龄林为0.259～1.414μmol·m^-2·s^-1;幼龄林年平均根系呼吸速率(1.198μmol.m^-2.s^-1)是中龄林的(0.937μmol.m^-2.s^-1)1.13倍。中龄林和幼龄林根系呼吸速率及根系呼吸占土壤总呼吸的比例季节变化规律基本一致,1年中基本呈现单峰曲线模式,高峰值出现在6月,之后逐渐下降至次年1月达最低值。幼龄林根系呼吸速率各月均明显高于中龄林,二者之间呼吸速率的最大差值出现在6月。幼龄林根系呼吸占土壤总呼吸的比例为31.79%～59.00%;而中龄林为23.50%～50.26%,变化幅度较幼龄林小。（6）中龄林和幼龄林根系呼吸速率与土壤5 cm内温度相关性显著。指数相关回归可以说明土壤温度对根系呼吸速率季节变化的影响,幼龄林达85.10%,中龄林达90.34%,中龄林根系呼吸对土壤温度的敏感程度大于幼龄林。根系呼吸速率与土壤含水量之间的相关性较差。在温度较低的情况下,土壤高含水量并没有促进根系的呼吸,但与土壤温度互作可能对林木根系呼吸产生较为显著的促进效果,这方面还需进一步研究。（7）中龄林根系呼吸速率与其细根生物量均呈线性正相关关系（p＜0.05）,可以说明常绿阔叶林细根生物量对根系呼吸速率影响达72.52%。但幼龄林根系呼吸速率与细根生物量相关性不显著,仅能解释其细根生物量对根系呼吸速率影响的39.65%。更多还原

【Abstract】 In order to understand the role of fine-root in forest ecosystems,fine-root biomass and related nutrients in a subtropical forest were studied in Xiaokeng forested watershed of Southern Anhui.The combining complementary methods,soil drilling law and inner growth law,were used to study fine root biomass distribution and fine-root biomass growth in the subtropical evergreen broad-leaved forest.The major research contents included（a） the seasonal patterns of fine-root biomass and related nutrient contents（N,P,K,Ca,Na, Mg,Fe）;（b） fine-root biomass growth;（3） root and soil respiration rate using Li-6400 CO₂ analyzer in the different development stages of the subtropical evergreen broad-leaved forest.The results from the study are shown as follows.（1） The fine-root biomass was greater in the surface soil layer than in the low ones for all sampling stands in subtropical evergreen broad-leaved forest.The fine-root biomass was 3.825 t hm^-2 in the mid-aged stand（40-yr）,which was similar to that(3.768 t hm^-2) in the young stand（18-yr）.The changes of fine-root biomass apeared largerly seasonal fluctuation,and the highest value for both mid-aged and young stands were in June.（2） The annual production of fine-root in the mid-aged stand was 1.394 t hm^-2 a^-1,which was very close to that of the young stand.The turnover rates of fine-root were,respectively, 0.36 and 0.37 for the evergreen broad-leaved species in mid-aged and young stands.The production of fine-roots varied seasonally,with the range（monthly average） of 0.031～0.228 t hm^-2 a^-1.The largest growth appeared in 3～6 months.（3） The contents of N,P,K,Ca,Mg,Na and Fe and their storages in fine-root were gradually decreased from surface to lower soil layer.There existed significant difference in fine-root biomass between different aged stands.The nutrient content of fine-root in the mid-aged stand were ranked by Fe＞Ca＞N＞K＞Na＞Mg＞P,while were Ca＞F＞K＞N＞Mg＞Na＞P for the young stand.The contents of N,P,K,Na in fine-root were hardly changed annually.However,the content of Ca in fine-root of evergreen broad-leaved trees in both mid-aged and young stand showed significant fluctuation,with the peak values in June and Novenber.Mg and Fe contents showed an abvious seasonal change with the maximum in September and the minimum in January.（4） The nutrient storages of N,P,K,Ca,Na,Mg,Fe of fine-root biomass were gradually decreased from surface to low soil layer,with significant difference between the mid-aged the mid-aged and young stands.The amounts of N,P,K,Na,Fe in fine-roots biomass were higher in the young stand than in the mid-aged stand.The seasonal pattern of nutrient storage in fine-root biomass in mid-aged stand was similar to that in the young stand.（5） The root respiration rate of mid-aged was in the range of 0.259～1.414μmol m^-2 s^-1 and that of young stand was 0.412～1.970μmol m^-2 s^-1,respectively.Te annual average rate of root respiration of young stand(1.198μmol m^-2 S^-1) was 1.13 times as great as that of mid-aged stand(0.937μmol m^-2 s^-1).The root respiration of mid-aged stand and young stand showed similar seasonal change.The percentage of root respiration to soil total respiration also showed the same patterns in both young and mid-aged stands.The basic model of seasonal change was a single peak curve,with the peak value in June.The root respiration rate of young stand was significantly higher than that of mid-aged stand.The proportion of root respiration to soil total respiration in young stand was in range of 31.79%～59.00%,while 23.50%～50.26%in mid-aged stand.（6） The root respiration in both mid-aged and young stands were significantly correlated to soil temperature at 5 cm.The root respiration of mid-aged stand was greater sensitive to the soil temperature than young stand.However,the root respiration was poorly related to the soil moisture.The interaction between soil moisture and temperature was likely to play a significantly effect to promoting root respiration,which needed further study.（7） The root respiration of mid-aged stand was significant with fine root biomass（p＜0.05）,which could explain 72.52%on the effect of fine root biomass,and none was the young stand.更多还原