【作者】 张凯；

【导师】 徐小牛；

【作者基本信息】 安徽农业大学 ， 森林培育， 2010， 博士

【摘要】 城市生态环境由于受到人为活动较大强度的干扰,其空气、水分、热量、土壤条件都具有不同于森林生态系统的特性,特别是绿地土壤的特性更是园林树木能否良好生长的重要影响因素。本研究选取生长于合肥市城市环境中的主要园林树木,通过分析其养分季节动态变化、养分利用效率、养分再吸收比例和氮磷比等指标以及园林树木树冠下土壤部分化学性质和碳氮转化特点的研究,试图为园林树木的养护管理提供可行的管理措施和理论依据。合肥城市绿地土壤受到较大的人为扰动,特别是建筑垃圾等的污染严重。土壤缺乏自然发育层次,紧实、容重高,大多数土壤偏碱性。土壤具有明显的缺氮特征。磷的分布极不规律,不同地点差异极大。不同绿地的表层0-10 cm土壤,其pH (H20)的平均值为7.70、pH(KCl)的平均值为6.80,电导率(EC)的均值为147.6μS·cm-1。全氮含量变动在0.70-2.30 g·kg-1；全磷含量变动在64.18-3144.54 mg·kg-1;速效磷含量在1.05-130.30 mg·kg-1;钾含量为5.12-11.02 g·kg-1；钠含量为2.49-5.35 g·kg-1；钙含量为6.22-131.80 g·kg-1；镁含量为4.99-12.16 g·kg-1。表层0-10 cm土壤中,蜀山森林公园枫香林下可溶性有机碳(DOC)含量最高(234.48 mg·kg-1),而校园绿地枫香林DOC含量最低(96.66 mg-kg-1);表层10-30 cm土层中,蜀山马尾松林下DOC含量最高(105.91 mg·kg-1),而环城公园雪松林下的最低(75.35 mg·kg-1)。表层0-10cm土壤中,蜀山森林公园马尾松林铵态氮含量最高(14.28 mg·kg-1),而环城公园雪松林最低(4.51 mg·kg-1);表层10-30 cm土层中,蜀山森林公园马尾松铵态氮含量最高(13.27 mg·kg-1),而环城公园雪松林最低(3.05 mg·kg-1)。表层0-10cm土壤中,校园绿地雪松林硝态氮含量最高(15.80 mg·kg-1),而蜀山森林公园马尾松枫香混交林最低(7.42 mg·kg-1);表层10-30 cm土层中,校园绿地雪松林硝态氮含量最高(14.63 mg·kg-1),而蜀山森林公园马尾松枫香混交林最低(6.37mg·kg-1).现场培养结果显示,校园绿地雪松林(UCC)0-10 cm土壤DOC转化速率为269.75μg·kg-1·d-1,10-30 cm土壤为-323.11μg·kg-1·d-1。移位交换培养试验显示,校园绿地雪松林下0-10 cm土壤移植于蜀山马尾松林(SPM)和环城公园雪松林(HPC)下培养的土壤DOC转化速率分别为420.75μg·kg-1·d-1和195.54μg·kg-1·d-1,而10-30 cm土壤则分别为-236.19μg·kg-1·d-1和-169.58μg·kg-1·d-1。环城公园雪松林0-10 cm土壤DOC转化速率为20.61μg·kg-1·d-1,10-30 cm土壤为-16.34μg·kg-1·d-1。移位交换培养试验显示,环城公园雪松林0-10 cm土壤移植于校园绿地雪松林和蜀山马尾松林下培养的土壤DOC转化速率分别为70.29μg·kg-1·d-1和93.92μg·kg-1·d-1,而10-30 cm土壤则分别为51.64μg·kg-1·d-1和-123.54μg·kg-1·d-1。蜀山马尾松林0-10 cm土壤DOC转化速率为285.42μg·kg-1·d-1,10-30 cm土壤为-213.18μg·kg-1·d-1。移位交换培养试验显示,蜀山马尾松林0-10 cm土壤移植于校园绿地雪松林和环城公园雪松林下培养的土壤DOC转化速率分别为525.35μg·kg-1·d-1和689.79μg·kg-1·d-1,而10-30 cm土壤则分别为-182.76μg·kg-1·d-1和-211.71μg·kg-1·d-1。校园绿地枫香林(UCL)0-10 cm土壤DOC转化速率为8.17μg·kg-1·d-1,10-30 cm土壤为-254.82μg·kg-1·d-1。移位交换培养试验显示,校园绿地枫香林下0-10 cm土壤移植于蜀山枫香林(SPL)下培养的土壤DOC转化速率为49.93μg·kg-1·d-1,而10-30cm土壤为-337.91μg·kg-1·d-1。蜀山枫香林0-10 cm土壤DOC转化速率为-168.35μg·kg-1·d-1,10-30 cm土壤为290.21μg·kg-1·d-1。移位交换培养试验显示,蜀山枫香林0-10 cm土壤移植于校园绿地枫香林培养的土壤DOC转化速率为-21.33μg·kg-1·d-1,而10-30 cm土壤为270.93μg·kg-1·d-1。校园绿地雪松林0-10 cm土壤的氨化速率、硝化速率和矿化速率分别为-21.32μg·kg-1·d-1,50.86μg·kg-1·d-1和4.09μg·kg-1·d-1,10-30 cm土壤分别为-51.20μg·kg-1·d-1,39.14μg·kg-1·d-1和13.40μg·kg-1·d-1。移位交换培养试验显示,校园绿地雪松林下0-10 cm土壤移植于蜀山马尾松林和环城公园雪松林下培养的土壤的净氨化速率分别为1.78μg·kg-1·d-1和-21.35μg·kg-1·d-1,10-30 cm土壤分别为-48.81μg·kg-1·d-1和-56.27μg·kg-1·d-1;0-10 cm土壤净硝化速率分别为61.53μg·kg-1·d-1和47.95μg·kg-1·d-1,10-30cm土壤分别为20.19μg·kg-1·d-1和64.78μg·kg-1·d-1; 0-10 cm土壤净矿化速率分别为6.07μg·kg-1·d-1和9.59μg·kg-1·d-1,10-30 cm土壤分别为28.62μg·kg-1·d-1 and 25.53μg·kg-1·d-1。环城公园雪松林0-10 cm土壤的氨化速率、硝化速率和矿化速率分别为-33.81μg·kg-1·d-1,75.09μg·kg-1·d-1和41.29μg·kg-1·d-1,10-30 cm土壤分别为-21.06μg·kg-1·d-1,65.97μg·kg-1·d-1和44.91μg·kg-1·d-1。移位交换培养试验显示,环城公园雪松林下0-10 cm土壤移植于校园绿地雪松林和蜀山马尾松林下培养的土壤的净氨化速率分别为-34.75μg·kg-1·d-1和-32.91μg·kg-1·d-1,10-30 cm土壤分别为-23.24μg·kg-1·d-1和-2.47μg·kg-1·d-1; 0-10 cm土壤净硝化速率分别为51.92μg·kg-1·d-1和83.08μg·kg-1·d-1,10-30 cm土壤分别为75.69μg·kg-1·d-1和57.10μg·kg-1·d-1; 0-10cm土壤净矿化速率分别为17.17μg·kg-1·d-1和50.18μg·kg-1·d-1,10-30 cm土壤分别为26.22μg·kg-1·d-1 and 27.31μg·kg-1·d-1。蜀山马尾松林0-10 cm土壤的氨化速率、硝化速率和矿化速率分别为-124.14μg·kg-1·d-1,81.92μg·kg-1·d-1和-42.23μg·kg-1·d-1,10-30 cm土壤分别为-121.17μg·kg-1·d-1,39.51μg·kg-1·d-1和-40.83μg·kg-1·d-1。移位交换培养试验显示,蜀山马尾松林下0-10 cm土壤移植于校园绿地雪松林和环城公园雪松林下培养的土壤的净氨化速率分别为-141.17μg·kg-1·d-1和-149.14μg·kg-1·d-1,10-30 cm土壤分别为-127.18μg·kg-1·d-1和-124.12μg·kg-1·d-1; 0-10 cm土壤净硝化速率分别为139.01μg·kg-1·d-1和132.23μg·kg-1·d-1,10-30 cm土壤分别为90.82μg·kg-1·d-1和75.74μg·kg-1·d-1; 0-10cm土壤净矿化速率分别为-2.16μg·kg-1·d-1和-16.91μg·kg-1·d-1,10-30 cm土壤分别为-18.18μg·kg-1·d-1和-48.38μg·kg-1·d-1。校园绿地枫香林0-10 cm土壤的氨化速率、硝化速率和矿化速率分别为13.66μg·kg-1·d-1,155.66μg·kg-1·d-1和169.32μg·kg-1·d-1,10-30 cm土壤分别为-18.13μg·kg-1·d-1,137.24μg·kg-1·d-1和119.11μg·kg-1·d-1。移位交换培养试验显示,校园绿地枫香林0-10 cm土壤移植于蜀山枫香林下培养的土壤的净氨化速率为-32.54μg·kg-1·d-1,10-30 cm土壤为-32.81μg·kg-1·d-1; 0-10 cm土壤净硝化速率为116.24μg·kg-1·d-1,10-30 cm土壤为45.55μg·kg-1·d-1; 0-10 cm土壤净矿化速率为83.69μg·kg-1·d-1,10-30 cm土壤为12.74μg·kg-1·d-1。蜀山枫香林0-10 cm土壤的氨化速率、硝化速率和矿化速率分别为-31.53μg·kg-1·d-1,13.45μg·kg-1·d-1和-18.08μg·kg-1·d-1,10-30 cm土壤分别为-46.97μg·kg-1·d-1,5.97μg·kg-1·d-1和-41.00μg·kg-1·d-1。移位交换培养试验显示,蜀山枫香林0-10 cm土壤移植于校园绿地枫香林下培养的土壤的净氨化速率为-35.16μg·kg-1·d-1,10-30 cm土壤为-27.90μg·kg-1·d-1; 0-10 cm土壤净硝化速率为0.10μg·kg-1·d-1,10-30 cm土壤为69.21μg·kg-1·d-1; 0-10 cm土壤净矿化速率为-35.06μg·kg-1·d-1,10-30 cm土壤为41.31μg·kg-1·d-1。不同林分表层土壤移位培养,氮素矿化速率发生明显变化,表明土壤氮素矿化作用不仅受控于基质特性,而且受到环境条件,特别是温度的强烈影响。表层0-10 cm土壤中,校园绿地枫香林土壤微生物量氮含量高达104.94 mg·kg-1,而校园绿地雪松林仅12.00 mg·kg-1; 10-30 cm土层中,蜀山公园马尾松枫香混交林的土壤微生物量氮含量最高,达80.28 mg·kg-1,而校园绿地雪松林最低(15.13 mg·kg-1)。不同林分土壤微生物量氮差异明显,但是,各林分的0-10 cm与10-30 cm土层之间没有显著差异。针叶树种的磷利用效率显著高于其他养分元素,钙利用效率最低。常见针叶树的NUEN变动范围为59.88-149.48 g·g-1; NUEP为460.83-4545.45 g·g-1; NUEK为152.67-877.19 g·g-1；NUENa为283.29-467.29 g·g-1；NUECa为39.56-262.47 g·g-1；NUEMg为196.46-316.46 g·g-1。落叶阔叶树种的NUEN变动范围为47.53-175.44 g·g-1；NUEP为303.95-4617.59 g·g-1；NUEK为50.94-297.97 g·g-1；NUENa为211.69-970.87 g·g-1；NUECa为39.87-189.04 g·g-1；NUEMg为109.60-353.61 g·g-1。常绿阔叶树种的NUEN变动范围为35.69-172.41 g·g-1；NUEP为521.71-4000.00g·g-1;NUEK为76.76-559.28 g·g-1；NUENa为219.88-574.71 g·g-1；NUECa为41.53-117.65g·g-1；NUEMg变为158.23-365.50 g·g-1。针叶树种中N：P比最高的为雪松,达27.52,最低的为铺地柏(8.26)。落叶阔叶树种N：P比波动在6.21(银杏)-19.95(麻栎)之间,常绿阔叶树种N：P比最大的为合作化路的香樟,达17.37,最低的为校园绿地小叶黄杨(10.15)。总体来看,所调查的树种中,N：P比小于14的有22种,占总数的46.8%；N：P比介于14-16之间的有15种,占总数的31.9%；N：P比大于16的有10种,占到总数的21.3%。更多还原

【Abstract】 The air, moisture, heat quantity and soil in the urban area were significantly different from those in forest ecosystem because of long-term human disturbances. The characteristics of urban soils were the important controls of the growth of urban trees. Nutrient seasonal dynamics, nutrient use efficiency, nutrient resorption and N:P ratio of the major urban trees, some soil chemical properties and the characteristics of carbon and nitrogen transformation of the different urban green-lands in Hefei were studied in order to find some orderlinesses which were useful for urban tree management.The soils under urban green-lands in Hefei were badly disturbed by human activities, particularly the pollution from architectural garbage. Urban soil could trend to be alkaline. Urban soils were poor in N. The distribution of P was irregular. The mean pH (H2O) in 0-10 cm soil was 7.70, and pH (KCl) was 6.80. The mean EC in 0-10 cm soil was 147.58μS·cm-1. Total nitrogen concentrations varied from 0.70 to 2.30 g·kg-1. Total phosphorus concentrations varied from 64.18 to 3144.54 mg·kg-1 and available phosphorus varied from 1.05 mg·kg-1 to 130.30 mg·kg-1. Total potassium concentrations varied from 5.12 to 11.02 g·kg-1. Total sodium concentrations varied from 2.49 to 5.35 g·kg-1. Total calcium concentrations varied from 6.22 to 131.80 g·kg-1. Total magnesium concentrations varied from 4.99 to 12.16 g·kg-1.The concentration of DOC in the 0-10 cm soil was the highest in the Liquidamba formosana forest in Shushan park (SPL; 234.48 mg·kg-1) and the lowest in the L. formosana forest on the university campus (UCL; 96.66 mg·kg-1), while for 10-30 cm soil the highest DOC was found in Pinus massoniana forest in Shushan park (SPP; 105.91 mg·kg-1) and the lowest in Cedrus deodara forest in Huancheng park (HPC; 75.35 mg·kg-1).The concentrations of extractable NH4+in the 0-10 cm and 10-30 cm soil were the highest in SPP site (14.28 mg·kg-1 and 13.27 mg·kg-1). The soil under HPC site had the lowest concentrations of extractable NH4+in both 0-10 cm (4.51 mg·kg-1) and 10-30 cm (3.05 mg·kg-1).The concentration of extractable NO3- in the 0-10 cm soils was the highest in HPC site (15.80 mg·kg-1) and the lowest in SPP and SPL sites (7.42 mg·kg-1), while for 10-30 cm soil the highest extractable NO3-was found in C. deodara forest on the campus (UCC; 14.63 mg·kg-1) and the lowest in SPP and SPL sites (6.37 mg·kg-1). Based on the in situ incubation experiment, the annual net rate of DOC was 269.75μg·kg-1·d-1 for 0-10 cm and -323.11μg·kg-1·d-1 for 10-30 cm in UCC site. In reciprocal transplant incubation, the annual net rates of DOC were, respectively,420.75μg·kg-1·d-1 and 195.54μg·kg-1·d-1 for 0-10 cm,-236.19μg·kg-1·d-1 and -169.58μg·kg-1·d-1 for 10-30 cm soil from UCC incubated in both SPP and HPC sites.The annual net rate of DOC was 20.61μg·kg-1·d-1 for 0-10 cm and -16.34μg·kg-1·d-1 for 10-30 cm in HPC site. In reciprocal transplant incubation, the annual net rate of DOC were, respectively,70.29μg·kg-1·d-1 and 93.92μg·kg-1·d-1 for 0-10 cm,51.64μg·kg-1·d-1 and -123.54μg·kg-1·d-1 for 10-30 cm soil from HPC incubated in both UCC site and SPP sites.The annual net rate of DOC was 285.42μg·kg-1·d-1 for 0-10 cm and -213.18μg·kg-1·d-1 for 10-30 cm in SPP site. In reciprocal transplant incubation, the annual net rates of DOC were, respectively,525.35μg·kg-1·d-1 and 689.79μg·kg-1·d-1 for 0-10 cm,-182.76μg·kg-1·d-1 and -211.71μg·kg-1·-1 for 10-30 cm soil from SPP site incubated in both UCC site and HPC sites.The annual net rate of DOC was 8.17μg·kg-1·d-1 for 0-10 cm and -254.82μg·kg-1·d-1 for 10-30 cm in UCL site. In reciprocal transplant incubation, the annual net rates of DOC were 49.93μg·kg-1·d-1 for 0-10 cm,-337.91μg·kg-1·d-1 for 10-30 cm soil from UCL site incubated in SPL site.The annual net rate of DOC was -168.35μg·kg-1·d-1 for 0-10 cm and 290.21μg·kg-1·d-1 for 10-30 cm soil in SPL site. In reciprocal transplant incubation, the annual net rate of DOC were -21.33μg·kg-1·d-1 for 0-10 cm,270.93μg·kg-1·d-1 for 10-30 cm soil from SPL site incubated in UCL site.The annual net rates of ammonification, nitrification and N mineralization were, respectively,-21.32μg·kg-1·d-1,50.86μg·kg-1·d-1 and 4.09μg·kg-1·d-1 for 0-10 cm in UCC site; and for 10-30 cm soil,-51.20μg·kg-1·-1,39.14μg·kg-1·d-1 and 13.40μg·kg-1·d-1. In reciprocal transplant incubation, the net annual rates of ammonification were, respectively, 1.78μg·kg-1·d-1 and -21.35μg·kg-1·d-1 for 0-10 cm,-48.81μg·kg-1·d-1 and -56.27μg·kg-1·d-1 for 10-30 cm soil from UCC site incubated in both SPM and HPC sites. The net annual nitrification rate were, respectively,61.53μg·kg-1·d-1 and 47.95μg·kg-1·d-1 for 0-10 cm,20.19μg·kg-1·d-1 and 64.78μg·kg-1·d-1 for 10-30 cm soil from UCC site incubated in both SPM and HPC sites. The net annual rates of N mineralization were, respectively,6.07μg·kg-1·d-1 and 9.59μg·kg-1·d-1 for 0-10 cm,28.62μg·kg-1·d-1 and 25.53μg·kg-1·d-1 for 10-30 cm soil from UCC site incubated in both SPM and HPC sites. The annual net rates of ammonification, nitrification and N mineralization were, respectively,-33.81μg·kg-1·d-1,75.09μg·kg-1·d-1 and 41.29μg·kg-1·d-1 for 0-10 cm in HPC site; and for 10-30 cm soil,-21.06μg·kg-1·d-1,65.97μg·kg-1·d-1 and 44.91μg·kg-1·d-1. In reciprocal transplant incubation, the net annual rates of ammonification were, respectively,-34.75μg·kg-1·d-1 and -32.91μg·kg-1·d-1 for 0-10 cm,-23.24μg·kg-1·d-1 and-2.47μg·kg-1·d-1 for 10-30 cm soil incubated in both UCC and SPM sites. The net annual nitrification rate were, respectively,51.92μg·kg-1·d-1 and 83.08μg·kg-1·d-1 for 0-10 cm, 75.69μg·kg-1·d-1 and 57.10μg·kg-1·d-1 for 10-30 cm soil incubated in both UCC and SPM sites. The net annual rates of N mineralization were, respectively,17.17μg·kg-1·d-1 and 50.18μg·kg-1·d-1 for 0-10 cm,26.22μg·kg-1·d-1 and 27.31μg·kg-1·d-1 for 10-30 cm soil incubated in both UCC and SPM sites.The annual net rates of ammonification, nitrification and mineralization were, respectively,-124.14μg·kg-1·d-1,81.92μg·kg-1·d-1 and -42.23μg·kg-1·d-1 for 0-10 cm in SPP site; and for 10-30 cm soil,-121.17μg·kg-1·d-1,39.51μg·kg-1·d-1 and -40.83μg·kg-1·d-1. In reciprocal transplant incubation, the net annual rates of ammonification were, respectively,-141.17μg·kg-1·d-1 and -149.14μg·kg-1·d-1 for 0-10 cm,-127.18μg·kg-1·d-1 and -124.12μg·kg-1·d-1 for 10-30 cm soil incubated in both UCC and HPC sites. The net annual nitrification rate were, respectively,139.01μg·kg-1·d-1 and 132.23μg·kg-1·d-1 for 0-10 cm,90.82μg·kg-1·d-1 and 75.74μg·kg-1·d-1 for 10-30 cm soil incubated in both UCC and HPC sites. The net annual rates of N mineralization were, respectively,-2.16μg·kg-1·d-1 and -16.91μg·kg-1·d-1 for 0-10 cm,-18.18μg·kg-1·d-1 and-48.38μg·kg-1·d-1 for 10-30 cm soil incubated in both UCC and HPC sites.The annual net rates of ammonification, nitrification and N mineralization were, respectively,13.66μg·kg-1·d-1,155.66μg·kg-1·d-1 and 169.32μg·kg-1·d-1 for 0-10 cm in UCL site; and for 10-30 cm soil,-18.13μg·kg-1·d-1,137.24μg·kg-1·d-1 and 119.11μg·kg-1·d-1.In reciprocal transplant incubation, the net annual rate of ammonification was-32.54μg·kg-1·d-1 for 0-10 cm,-32.81μg·kg-1·d-1 for 10-30 cm soil incubated in SPL site. The net annual nitrification rate was 116.24μg·kg-1·d-1 for 0-10 cm,45.55μg·kg-1·d-1 for 10-30 cm soil incubated in SPL site. The net annual rate of N mineralization was 83.69μg·kg-1·d-1 for 0-10 cm,12.74μg·kg-1·d-1 for 10-30 cm soil incubated in SPL site.The annual net rates of ammonification, nitrification and mineralization were, respectively,-31.53μg·kg-1·d-1,13.45μg·kg-1·d-1 and -18.08μg·kg-1·d-1 for 0-10 cm in SPL site; and for 10-30 cm soil,-46.97μg·kg-1·d-1,5.97μg·kg-1·d-1 and -41.00μg·kg-1·d-1. In reciprocal transplant incubation, the net annual rate of ammonification was -35.16 μg·kg-1·d-1 for 0-10 cm,-27.90μg·kg-1·d-1 for 10-30 cm soil incubated in UCL site. The net annual nitrification rate was 0.10μg·kg-1·d-1 for 0-10 cm,69.21μg·kg-1·d-1 for 10-30 cm soil incubated in UCL site. The net annual rate of N mineralization was -35.06μg·kg-1·d-1 for 0-10 cm,41.31μg·kg-1·d-1 for 10-30 cm soil incubated in UCL site.Results from the experiment showed that N transformation varied significantly by the reciprocal transplant incubation for the different sampling stands. It suggests that soil N transformation is comtrolled by the substrate quality, and is strongly affected by the environmental condition particullarly temperature as well.The annual mean concentration of soil microbial biomass nitrogen (SMBN) in the 0-10 cm soil was the highest in the Liquidamba formosana forest of campus (104.94 mg-kg-1) and the lowest in the Pinus massoniana forest of campus (12.00 mg-kg-1), while for 10-30 cm soil the highest SMBN was found in Pinus massoniana and Liquidamba formosana mixed forest of Shushan park (80.28 mg-kg-1) and the lowest in the Pinus massoniana forest of campus (15.13 mg-kg-1). There existed a significant difference in SMBN amongst the sampling stands. However, no significant differences in SMBN occurred between 0-10 cm and 10-30 cm soils for all the sampling stands.Nitrogen use efficiency (NUEN) of the common conifers ranged from 59.88 to 149.48 g·g-1, for NUEP from 460.83 to 4545.45 g·g-1, NUEK from 152.67 to 877.19 g·g-1, NUECa from 39.56 to 262.47 g·g-1, NUEMg from 196.46 to 316.46 g·g-1, NUENa from 467.29 to 283.29 g·g-1. NUEP was significantly higher than the other nutrient elements.NUEN in leaf litter for the different deciduous broad-leaved tree species in urban Hefei ranged from 47.53 to 175.44 g·g-1, NUEP from 303.95 to 4617.59 g·g-1, NUEK from 50.94 to 297.97 g·g-1, NUECa from 39.87 to 189.04 g·g-1, NUEMg from 109.60 to 353.61 g·g-1, and NUENa from 211.69 to 970.87 g·g-1.NUEN in leaf litter for the different evergreen broad-leaved tree species in urban Hefei ranged from 35.69 to 172.41 g·g-1, NUEP from 521.71 to 4000.00 g·g-1, NUEK from 76.76 to 559.28 g·g-1, NUENa from 219.88 to 574.71 g·g-1, NUECa from 41.53 to 117.65 g·g-1, NUEMg from 158.23 to 365.50 g·g-1.Cedrus deodara in UCC site had the highest N:P stoichiometrical ratio (27.52) and Sabina procumbens the lowest (8.26) in needles among the different coniferous species in urban Hefei. The N:P ratio varied from 6.21 (Ginkgo biloba)to 19.95 (Quercus acutissima) in leaves for the different deciduous broad-leaved tree species sampled in urban Hefei. Within the evergreen broadleaved tree species, Cinnamomum camphora in the Hezuohua Road had the highest N:P ratio (17.37) and Buxus bodinieri in the campus the lowest (10.15). Within the species studied,22 species (46.81%), with N:P ratio<14, were in N limitation; and 10 species (21.28%) were in P limitation (N:P ratio>16). There were 15 species (31.91%) with N:P ratio in a range of 14-16, indicating that those species were limited by both N and P.更多还原