共查询到14条相似文献，搜索用时 46 毫秒
1.
该研究2011年1月开始在鼎湖山针阔叶混交林(混交林)进行模拟酸雨实验,设置4个不同处理水平,即对照(CK)(pH为4.5左右的天然湖水)、T_1(pH=4.0)、T_2(pH=3.25)和T_3(pH=2.5)。2013年1—12月对不同酸雨强度处理下的森林凋落物CO_2释放速率进行为期1 a的连续观测,探讨酸雨对混交林凋落物C排放的影响。结果表明:凋落物CO2释放通量在对照样方为(1 507.41±155.19) g CO_2·m~(-2)·a~(-1),其中湿季和旱季分别占年通量的68.7%和31.3%。模拟酸雨抑制了森林凋落物CO_2释放,与CK相比,T_2和T_3处理下的CO_2释放通量分别显著降低15.4%和42.7%(P0.05);且这种抑制作用具有季节差异性,处理间的显著差异只出现在湿季。凋落物CO_2释放速率与土壤温度和土壤湿度分别呈显著指数相关和显著直线相关,同时,酸雨处理降低了凋落物CO_2释放的温度敏感性。混交林凋落物CO_2释放在模拟酸雨下的抑制效应与土壤累积酸化而导致的土壤微生物活性变化有关,表现为模拟酸雨作用下土壤pH值和微生物量碳显著下降。上述结果说明酸雨是影响混交林土壤碳循环的重要因子之一。 相似文献
2.
长白山次生针阔混交林叶凋落物中有机物分解与碳、氮和磷释放的关系 总被引：20，自引：0，他引：20
采用分解袋法,研究了长白山次生针阔混交林内9种树种叶凋落物34个月的分解过程.结果表明:在次生针阔混交林中,不同树种叶凋落物的初始N和P浓度存在很大差异,叶凋落物分解速率(k)与初始N浓度和C/N显著相关.有机物剩余百分率与C剩余百分率呈显著的线性正相关关系,与N和P剩余百分率之间呈显著的二项式回归关系. N和P剩余百分率在初期阶段随有机物分解而增加,达到峰值后逐渐降低. 随着有机物剩余百分率的下降,C/N和C/P均呈逐渐降低趋势,各种叶凋落物之间C/N和C/P的差异逐渐减小,分解末期分别趋近于23和350. 随有机物剩余百分率的降低, N/P变化不明显,当有机物剩余百分率低于25%时,不同树种叶凋落物之间N/P差异显著下降. 有机物剩余百分率可用来预测C、N和P的剩余百分率. 相似文献
3.
择伐对小兴安岭针阔叶混交林土壤呼吸的影响 总被引：1，自引：0，他引：1
利用LI-8100土壤CO2排放通量全自动测量系统,测定了黑龙江省带岭林业局东方红林场不同采伐强度林地的土壤表面CO2通量和土壤表层10 cm处的温度和湿度,研究了择伐作业后林地土壤表面CO2通量变化及影响因素.结果表明：伐后林分土壤温度和湿度与土壤表面CO2通量季节变化呈较好的相关关系,解释了土壤呼吸的68%～98%;择伐作业使林地表面CO2通量增加,年均增幅在7.17%～26.89%;采伐强度与土壤表面CO2通量呈显著的二次相关关系（R2=0.961）.土壤有机质含量和采伐强度是导致择伐后土壤表面CO2通量变化的主要影响因子. 相似文献
4.
2010年7-12月,选取鼎湖山国家级自然保护区亚热带针阔叶混交林,采用全因子控制试验,研究不同类型的凋落物(针叶和阔叶凋落物)添加及氮处理(加氮模拟氮饱和、减氮模拟根吸收)对表层(0～10 cm)和下层(20～30 cm)土壤有机质分解(呼吸)的影响.结果表明： 2010年7-11月间,两种凋落物的添加使土壤-凋落物系统的呼吸速率显著增加,但这种影响在12月消失.减氮和加氮处理均显著增加了土壤-凋落物系统的呼吸.叶凋落物短期内完全分解,对土壤碳分解和积累的影响十分有限,可能不是该系统中土壤有机质的主要来源.通过减少土壤可利用氮模拟根系对氮的吸收能够明显促进土壤有机质的分解. 相似文献
5.
为了进一步探讨土壤凋落物层对土壤呼吸的影响,用Li-6400对大兴安岭北部3种林型(白桦-落叶松林、樟子松-落叶松林和落叶松纯林)自然状态的土壤呼吸(RS)、去凋落物后的土壤呼吸(RD)以及凋落物呼吸(RL)进行测定,结果表明:凋落物层的去除会使土壤呼吸速率降低,3种林型观测期内平均RS分别为7.32μmol m-2 s-1、8.55μmol m-2 s-1和6.66μmol m-2 s-1,平均RD分别为6.46μmol m-2 s-1、7.98μmol m-2 s-1和5.74μmol m-2 s-1。但去除凋落物后的土壤总呼吸速率较自然状态下分别升高了13.85%、16.21%和13.73%;凋落物的去除并不影响... 相似文献
6.
杉木人工林凋落物量对氮沉降增加的初期响应 总被引：10，自引：1，他引：10
通过野外模拟试验,研究了杉木人工林凋落物对氮沉降增加的初期响应。试验设计为4种处理,分别为N0(0kgN.hm-2.a-1,对照)、N1(60kgN.hm-2.a-1)、N2(120kgN.hm-2.a-1)、N3(240kgN.hm-2.a-1),3次重复。通过2年监测发现,对照样地的年凋落量为2427.51kg.hm-2,而经N1、N2、N3处理后,其年凋落物量分别为2238.10、2286.66和2599.50kg.hm-2。表明高氮(N3)处理显著增加了杉木林凋落物量(P<0.05),而中低氮处理(N1、N2)没有显著影响。各处理的总凋落物量表现出明显的季节动态,在2、5和7月出现3个比较明显的峰值。在凋落物的组成中,落叶占总凋落量的70.49%～73.67%,其次分别为落枝(19.38%～20.39%)、碎屑物(4.98%～7.70%)、落果(1.11%～2.16%)和树皮(0.29%～0.33%)。LSD多重比较显示,N3处理对落叶和落果产生显著影响,对其它组分的影响不明显。 相似文献
7.
To assess the long-term effects of atmospheric deposition on forest floor chemical composition, we took quantitative samplings of L-(Oi), F-(Oe), and H-(Oa) layers at an old-growth sugar maple–yellow birch stand on a till soil at the Turkey Lakes Watershed near Lake Superior, Ontario, Canada, in 1981 and 1996. We then assessed these samples for contents of organic matter (OM), total N, K, Ca, Mg, S, and Na, and exchangeable NH4 +, NO3 −, K+, Ca2+, Mg2+, SO4 2−, and Na+. Over the 15-year period, total OM and element contents remained unchanged, with the exception of N, which increased significantly from 61.3 kmol/ha in 1981 to 78.4 kmol/ha in 1996. On an area basis, there were significant increases in exchangeable Ca2+ (from 3.8 to 4.6 kmol/ha) and Na+ (from 0.05 to 0.08 kmol/ha) and decreases in exchangeable NH4 +-N (from 1.41 to 0.95 kmol/ha) and SO4 2−-S (from 1.29 to 0.96 kmol/ha). There were no significant differences in average annual litterfall OM, N, Ca, Mg, S or Na inputs between 1980 and 1985 and between 1992 and 1997. Average annual wet-only SO4 2−-S deposition during 1981–86 was 0.30; during 1992–97, it was 0.21 kmol/ha. Annual wet-only NO3 −-N averaged 0.33 kmol/ha during 1981–86 and was similar during 1992–97. Throughfall was less rich in SO4 2− and Ca2+, Mg2+, and Na+ during 1992–97 than earlier. Throughfall NH4 + and NO3 − fluxes were unchanged. Efflux of cations from the forest floor reflected reduced throughput of SO4 2−. Overall, the results suggest that in spite of atmospheric inputs, active biological processes—including litter input, fine-root turnover, and tree uptake—serve to impart stability to the mineral composition of mature sugar maple forest floor. Received 5 October 1999; accepted 25 October 2000. 相似文献
8.
城市水体包括城区内的自然水体和人工水体两大类。作为城市生态系统的重要组成部分,水体在缓解城市热岛效应(Urban Heat Island, UHI)上具有重要作用。研究城市热岛效应的现状,探讨水体对城市热岛的缓冲效应,为改善城市热岛效应和生态环境,并对城市进行合理的改造和规划提供理论依据。以长沙市中心城区为研究区域,以南北向贯穿长沙市的湘江河道作为主要研究对象,基于长沙市2016年7月Landsat 8 TIRS遥感影像采用大气校正法反演地表温度(Land Surface Temperature, LST),利用监督分类法获取其同步的城市化进程和土地利用类型,分析市区内地表温度及热岛效应的空间分布特征。同时,通过在湘江两侧建立多个尺度的缓冲区,并将其与地表温度分布及土地利用类型叠置,分析湘江为主的水体对长沙市热环境及各缓冲区的缓冲效应,结果表明:(1)长沙市城市建设格局与热岛效应空间分布基本相似,建筑用地热岛效应更高,极端地表温度达到53.8℃;水体、绿地和裸地的热岛效应相对较低,最低地表温度为16.0℃;(2)湘江对长沙市热岛效应具有缓冲作用,对长沙市热岛效应的平均缓冲距离为400 ... 相似文献
9.
《植物生态学报》2017,41(1):71
Aims The shrublands of northern China have poor soil and nitrogen (N) deposition has greatly increased the local soil available N for decades. Shrub growth is one of important components of C sequestration in shrublands and litterfall acts as a vital link between plants and soil. Both are key factors in nutrient and energy cycling of terrestrial ecosystems, which greatly affected by nitrogen (N) addition (adding N fertilizer to the surface soil directly). However, the effects and significance of N addition on C sequestration and litterfall in shrublands remain unclear. Thus, a study was designed to investigate how N deposition and related treatments affected shrublands growth related to C sequestration and litterfall production of Vitex negundo var. heterophylla and Spiraea salicifolia in Mt. Dongling region of China.
Methods A N enrichment experiment has been conducted for V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, including four N addition treatment levels (control (N0, 0 kg N·hm-2·a-1), low N (N1, 20 kg N·hm-2·a-1), medium N (N2, 50 kg N·hm-2·a-1) and high N (N3, 100 kg N·hm-2·a-1)). Basal diameter and plant height of shrub were measured from 2012-2013 within all treatments, and allometric models for different species of shrub’s live branch, leaf and root biomass were developed based on independent variables of basal diameter and plant height, which will be used to calculate biomass increment of shrub layer. Litterfall (litterfall sometimes is named litter, referring to the collective name for all organic matter produced by the aboveground part of plants and returned to the surface, and mainly includes leaves, bark, dead twigs, flowers and fruits.) also was investigated from 2012-2013 within all treatments.
Important findings The results showed 1) mean basal diameter of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were increased by 1.69%, 2.78%, 2.51%, 1.80% and 1.38%, 1.37%, 1.59%, 2.05% every year; 2) The height growth rate (the shrub height relative growth rate is defined with the percentage increase of plant height) of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were 8.36%, 8.48%, 9.49%, 9.83% and 2.12%, 2.86%, 2.36%, 2.52% every year, respectively. Thee results indicated that N deposition stimulated growth of shrub layer both in V. negundo var. heterophylla and S. salicifolia shrublands, but did not reach statistical significance among all nitrogen treatments. The above-ground biomass increment of shrub layer in the V. negundo var. heterophylla and S. salicifolia shrublands were 0.19, 0.23, 0.14, 0.15 and 0.027, 0.025, 0.032, 0.041 t C·hm-2·a-1 respectively, which demonstrated that short-term N addition had no significant effects on the accumulation of C storage of the two shrublands. The litter production of the V. negundo var. heterophylla and S. salicifolia communities in 2013 were 135.7 and 129.6 g·m-2 under natural conditions, respectively. Nitrogen addition promoted annual production of total litterfall and different components of litterfall to a certain extent, but did not reach statistical significance among all nitrogen treatments. Above results indicated that short-term fertilization, together with extremely low soil moisture content and other related factors, lead to inefficient use of soil available nitrogen and slow response of shrublands to N addition treatments. 相似文献
Methods A N enrichment experiment has been conducted for V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, including four N addition treatment levels (control (N0, 0 kg N·hm-2·a-1), low N (N1, 20 kg N·hm-2·a-1), medium N (N2, 50 kg N·hm-2·a-1) and high N (N3, 100 kg N·hm-2·a-1)). Basal diameter and plant height of shrub were measured from 2012-2013 within all treatments, and allometric models for different species of shrub’s live branch, leaf and root biomass were developed based on independent variables of basal diameter and plant height, which will be used to calculate biomass increment of shrub layer. Litterfall (litterfall sometimes is named litter, referring to the collective name for all organic matter produced by the aboveground part of plants and returned to the surface, and mainly includes leaves, bark, dead twigs, flowers and fruits.) also was investigated from 2012-2013 within all treatments.
Important findings The results showed 1) mean basal diameter of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were increased by 1.69%, 2.78%, 2.51%, 1.80% and 1.38%, 1.37%, 1.59%, 2.05% every year; 2) The height growth rate (the shrub height relative growth rate is defined with the percentage increase of plant height) of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were 8.36%, 8.48%, 9.49%, 9.83% and 2.12%, 2.86%, 2.36%, 2.52% every year, respectively. Thee results indicated that N deposition stimulated growth of shrub layer both in V. negundo var. heterophylla and S. salicifolia shrublands, but did not reach statistical significance among all nitrogen treatments. The above-ground biomass increment of shrub layer in the V. negundo var. heterophylla and S. salicifolia shrublands were 0.19, 0.23, 0.14, 0.15 and 0.027, 0.025, 0.032, 0.041 t C·hm-2·a-1 respectively, which demonstrated that short-term N addition had no significant effects on the accumulation of C storage of the two shrublands. The litter production of the V. negundo var. heterophylla and S. salicifolia communities in 2013 were 135.7 and 129.6 g·m-2 under natural conditions, respectively. Nitrogen addition promoted annual production of total litterfall and different components of litterfall to a certain extent, but did not reach statistical significance among all nitrogen treatments. Above results indicated that short-term fertilization, together with extremely low soil moisture content and other related factors, lead to inefficient use of soil available nitrogen and slow response of shrublands to N addition treatments. 相似文献
10.
Xiankai Lu Qinggong Mao Frank S. Gilliam Yiqi Luo Jiangming Mo 《Global Change Biology》2014,20(12):3790-3801
Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long‐term N deposition on soil acidification processes in tropical forests. We have established a long‐term N‐deposition experiment in an N‐rich lowland tropical forest of Southern China since 2002 with N addition as NH4NO3 of 0, 50, 100 and 150 kg N ha?1 yr?1. We measured soil acidification status and element leaching in soil drainage solution after 6‐year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid‐sensitive showing high acidification (pH(H2O)<4.0), negative water‐extracted acid neutralizing capacity (ANC) and low base saturation (BS,< 8%) throughout soil profiles. Long‐term N addition significantly accelerated soil acidification, leading to depleted base cations and decreased BS, and further lowered ANC. However, N addition did not alter exchangeable Al3+, but increased cation exchange capacity (CEC). Nitrogen addition‐induced increase in SOC is suggested to contribute to both higher CEC and lower pH. We further found that increased N addition greatly decreased soil solution pH at 20 cm depth, but not at 40 cm. Furthermore, there was no evidence that Al3+ was leaching out from the deeper soils. These unique responses in tropical climate likely resulted from: exchangeable H+ dominating changes of soil cation pool, an exhausted base cation pool, N‐addition stimulating SOC production, and N saturation. Our results suggest that long‐term N addition can contribute measurably to soil acidification, and that shortage of Ca and Mg should receive more attention than soil exchangeable Al in tropical forests with elevated N deposition in the future. 相似文献
11.
《植物生态学报》2018,42(1):95
土壤交换性盐基离子(Ca 2+、Mg 2+、K +、Na +)在维持土壤养分与缓冲土壤酸化中起着重要作用, 了解其对氮添加的响应有助于准确评估氮沉降背景下生态系统结构与功能的动态变化。然而, 目前关于土壤交换性盐基离子对氮添加响应的相关研究主要集中在酸性土中。鉴于目前在碱性土中研究相对较少的现状, 该研究以青藏高原高寒草原为研究对象, 依托氮添加控制实验平台, 通过连续3年(2014-2016)的测定, 考察了8个不同施氮水平(0、1、2、4、8、16、24、32 g·m -2·a -1)下土壤交换性盐基离子含量变化及其可能原因。结果显示: 随着施氮量的增加, 土壤交换性盐基离子, 尤其是Mg 2+与Na +含量显著降低。并且, 盐基离子含量与植物地上生物量显著负相关(p < 0.05), 说明氮添加通过促进植物生长, 加速植物对盐基离子的吸收, 进而导致土壤中盐基离子含量降低。此外, 盐基离子含量也与土壤无机氮含量呈显著负相关(p < 0.05)关系, 说明施氮还通过提高土壤中无机氮含量进而导致更多NH4 +与土壤吸附的盐基离子交换, 同时加剧NO3 -淋溶, 带走等电荷阳离子。需要指出的是, 虽然连续施氮导致土壤pH值下降, 但该土壤目前仍处于碳酸盐缓冲阶段, 说明通常在酸性土中报道的“因缓冲土壤酸化引起的盐基离子损失机制”在碱性土中并不成立。这些结果意味着持续的氮输入会造成碱性土中盐基离子损失, 进而影响土壤缓冲能力与植被生产力, 未来草原生态系统管理中应重视这一问题。 相似文献
12.
施肥和增水对弃耕草地土壤酸中和容量的影响 总被引：2，自引：0，他引：2
大气氮沉降增加是草地土壤酸化的主要原因。土壤酸缓冲性能作为评估土壤酸化的重要指标,对氮输入的响应受到降水与其他限制养分含量的影响。本研究以我国北方温带弃耕草地氮、磷、水添加试验13年后的土壤为对象,利用二次多项式模型拟合酸滴定曲线,计算了土壤酸缓冲容量(ABC)以及以pH 5.0和4.0为参比的土壤酸中和容量(ANC)。结果表明: 不增水处理下,单独加氮和同时添加氮磷均显著降低土壤pH,降低以pH 5.0和4.0为参比时的酸中和容量(ANCpH5.0和ANCpH4.0);单独加磷对土壤pH、ANCpH5.0和ANCpH4.0均无显著影响。增水处理下,加氮及加氮磷显著降低土壤pH、ANCpH5.0和ANCpH4.0;加磷显著降低土壤pH,但增加了ANCpH4.0,而对ANCpH5.0无显著影响。与不增水处理相比,增水处理对土壤pH、酸中和容量均具有显著的正效应。对于初始pH值不同的土壤,采用土壤酸中和容量比酸缓冲容量能更好地指示土壤抗酸化能力。 相似文献
13.
Selçuk Soyupak Coşkun Yurteri Labeeb Mukhallalati Başak Kiliç Serpil Kayin Koray Önder 《Soil & Sediment Contamination》1996,5(3):203-214
Potential soil acidification impacts of a proposed natural gas‐fired combined cycle power plant were assessed using an integrated approach coupling an atmospheric deposition model with soil acidification quantification. The deposition model was used to estimate the rates of nitrogen oxide (NOx) deposition on the air‐soil boundary. The expected changes in the soil column were then predicted by utilizing mechanistic and experimental methods, and the number of years required to reach critical pH values were predicted using the two methods mentioned above under different rates of acidic deposition. The number of years predicted by the mechanistic modeling approach was lower for all soils exhibiting calcareous character. 相似文献
14.
在湖南会同杉木林生态系统国家野外科学观测研究站试验基地的第Ⅲ集水区,对连作杉木林的凋落物量进行连续20a的定位观测,研究凋落物的组成特征、季节和长期动态变化格局.结果表明:连作杉木林从第8年起开始收集到凋落物,第8～20年间,凋落物量总体呈上升趋势,年平均生物量为(1109.86±117.27)kg·hm-2.凋落物中针叶、小枝、落果和碎屑所占比例分别为63.75%,25.87%,5.11%和2.19%.会同杉木人工林有明显的季节性凋落节律,1月至6月份,凋落物量总体上呈现上升趋势,从6月份至12月份总体上呈下降趋势,凋落物量的峰值出现在6月份,11月份则全年最低.凋落物与林龄呈显著的二次曲线相关,模拟凋落物量与林龄的关系,得到二次曲线方程关系:y=-10.06x2+361.1x-1747,R2=0.920, p<0.001.凋落物中的小枝、针叶、落果与林龄呈显著二次曲线方程关系(p<0.05),而碎屑与林龄的相关性不显著. 相似文献