The characteristics of throughfall and stemflow over one growing season were studied in a dark coniferous forest in the subalpine of the Western Sichuan. The results indicated that: 1) The distribution of precipitatio...The characteristics of throughfall and stemflow over one growing season were studied in a dark coniferous forest in the subalpine of the Western Sichuan. The results indicated that: 1) The distribution of precipitation by canopy was more relative to the rainfall, the higher the rainfall was, the more the throughfall and stemflow were, and the less the interception was; 2) The relationships between throughfall (T) and total rainfall (P) could be described significantly by a linear function (T=0.744P-0.937, R 2=0.954, p<0.001), while the reationship between crown interception (I) and total rainfall by a power function (I=0.759P 0.666, R 2=0.763, p<0.001); 3) The average canopy interception accounted for 35.8% of total rainfall and the average throughfall for 64.2%, and the average stemflow for 0.01%; 4) High water_hold capacity of moss on the surface of tree trunk and low rainfall intensity were the main reasons that the stemflow of the coniferous forest in the subalpine of Western Sichuan was less than other forests.展开更多
林冠截留是森林生态水文的重要环节,SWAT(Soil and Water Assessment Tool)模型对其模拟过程还较为粗糙,为了在流域水文模拟中更精细的刻画林冠截留过程从而得到更佳的模拟结果,以SWAT模型为基础,使用半理论林冠截留模型(Gash模型)与SWA...林冠截留是森林生态水文的重要环节,SWAT(Soil and Water Assessment Tool)模型对其模拟过程还较为粗糙,为了在流域水文模拟中更精细的刻画林冠截留过程从而得到更佳的模拟结果,以SWAT模型为基础,使用半理论林冠截留模型(Gash模型)与SWAT模型进行耦合,以天山林区为研究区对SWAT模型林冠截留模块进行优化改进。通过对改进前后的模拟结果进行对比分析,结果表明:1)SWAT模型和SWAT-Gash模型的R~2分别为0.59—0.83和0.65—0.86,NSE值分别为0.58—0.82和0.63—0.85,两种模型PBIAS为7.2%—17.1%,证明SWAT-Gash模型具有更好的适用性;2)相较于出山口径流数据,SWAT模型和SWAT-Gash模型的RMSD值分别为3.49—7.80 m^(3)/s和3.22—4.68 m^(3)/s,SWAT-Gash模型在校准期和验证期的皮尔逊相关系数分别为0.93和0.81,高于SWAT模型的0.91和0.77;3)基于分位数回归(QR)的不确定性分析表明,SWAT模型和SWAT-Gash模型验证期的P因子分别为0.93和0.96,R因子为1.26和1.19,95%不确定性置信区间平均宽度分别为13.50 m^(3)/s和12.86 m^(3)/s;4)SWAT模型与SWAT-Gash模型在验证期的月平均地表径流量分别为6.55 m^(3)/s和8.50 m^(3)/s,表明在该流域内原始SWAT模型会高估林冠截留量。以天山北坡中段林区为例对云杉森林的林冠截留进行精细化模拟,虽然对模型输入数据要求提高,林冠截留数据的收集增加了模型模拟的不确定性,但对本研究区基于物理过程的水文模拟精度提升明显,改进后模型与出山口实测径流数据一致性更强,可以为天山林区小流域水资源管理提供更可靠的依据。展开更多
森林土壤总氮矿化对冻融过程的响应机制尚不明确,氮矿化速率和转化情况尚缺乏定量刻画。通过土壤原位法与室内培养分析相结合,利用15N同位素稀释技术,研究冻融期间天山林区乔木林地、灌丛、草地3种群落类型土壤总氮矿化及转化累积量的动...森林土壤总氮矿化对冻融过程的响应机制尚不明确,氮矿化速率和转化情况尚缺乏定量刻画。通过土壤原位法与室内培养分析相结合,利用15N同位素稀释技术,研究冻融期间天山林区乔木林地、灌丛、草地3种群落类型土壤总氮矿化及转化累积量的动态,分析土壤总氮矿化速率与土壤温度、含水率及微生物量氮(MBN)的相互关系。结果表明:(1)冻融过程及群落类型对总氮矿化速率和MBN含量有极显著的影响(P<0.01),秋、春季冻融期的总氮矿化速率相比冻结期更高;(2)季节性冻融期间,乔木林地土壤总氨化累积量在3种群落类型中最高(163.9 kg N hm^-2 a^-1),秋、春冻融期占整个时期的比值约为66%;而总硝化累积量在3种群落类型中相差较小,秋、春冻融期占比均约为77.4%;(3)土壤温度和含水率显著影响总氮矿化速率、净氮矿化速率和MBN速率,随土壤温度增加,总氨化速率(林地和灌丛)显著升高(P<0.05);随土壤含水率增加,净氨化速率(灌丛)和净硝化速率(灌丛)显著降低(P<0.05)。通过揭示天山林区土壤总氮矿化速率(总氨化速率和总硝化速率)及转化累积量对冻融过程的响应情况,本研究为天山森林土壤中氮的生物地球化学过程提供了有价值的基础数据。展开更多
Spatial heterogeneity is an inherent characteristic of natural forest landscapes, therefore estimation of structural variability, including the collection and analyzing of field measurements, is a growing challenge fo...Spatial heterogeneity is an inherent characteristic of natural forest landscapes, therefore estimation of structural variability, including the collection and analyzing of field measurements, is a growing challenge for monitoring wildlife habitat di- versity and ecosystem sustainability. In this study, we investigated the combined influence of plot shape and size on the accuracy of assessment of conventional and rare structural features in two young-growth spruce-dominated forests in northwestern China. We used a series of inventory schemes and analytical approaches. Our data showed that options for sampling protocols, especially the selection of plot size considered in structural attributes measurement, dramatically af- fect the minimum number of plots required to meet a certain accuracy criteria. The degree of influence of plot shape is related to survey objectives; thus, effects of plot shape differ for evaluations of the ＂mean＂ or ＂representative＂ stand structural conditions from that for the range of habitat （in extreme values）. Results of Monte Carlo simulations suggested that plot sizes 〈0.1 ha could be the most efficient way to sample for conventional characteristics （features with relative constancy within a site, such as stem density）. Also, 0.25 ha or even larger plots may have a greater likelihood of capturing rare structural attributes （features possessing high randomness and spatial heterogeneity, such as volume of coarse woody debris） in our forest type. These findings have important implications for advisable sampling protocol （plot size and shape） to adequately capture information on forest habitat structure and diversity; such efforts must be based on a clear definition of which types are structural attributes to measure.展开更多
文摘The characteristics of throughfall and stemflow over one growing season were studied in a dark coniferous forest in the subalpine of the Western Sichuan. The results indicated that: 1) The distribution of precipitation by canopy was more relative to the rainfall, the higher the rainfall was, the more the throughfall and stemflow were, and the less the interception was; 2) The relationships between throughfall (T) and total rainfall (P) could be described significantly by a linear function (T=0.744P-0.937, R 2=0.954, p<0.001), while the reationship between crown interception (I) and total rainfall by a power function (I=0.759P 0.666, R 2=0.763, p<0.001); 3) The average canopy interception accounted for 35.8% of total rainfall and the average throughfall for 64.2%, and the average stemflow for 0.01%; 4) High water_hold capacity of moss on the surface of tree trunk and low rainfall intensity were the main reasons that the stemflow of the coniferous forest in the subalpine of Western Sichuan was less than other forests.
文摘森林土壤总氮矿化对冻融过程的响应机制尚不明确,氮矿化速率和转化情况尚缺乏定量刻画。通过土壤原位法与室内培养分析相结合,利用15N同位素稀释技术,研究冻融期间天山林区乔木林地、灌丛、草地3种群落类型土壤总氮矿化及转化累积量的动态,分析土壤总氮矿化速率与土壤温度、含水率及微生物量氮(MBN)的相互关系。结果表明:(1)冻融过程及群落类型对总氮矿化速率和MBN含量有极显著的影响(P<0.01),秋、春季冻融期的总氮矿化速率相比冻结期更高;(2)季节性冻融期间,乔木林地土壤总氨化累积量在3种群落类型中最高(163.9 kg N hm^-2 a^-1),秋、春冻融期占整个时期的比值约为66%;而总硝化累积量在3种群落类型中相差较小,秋、春冻融期占比均约为77.4%;(3)土壤温度和含水率显著影响总氮矿化速率、净氮矿化速率和MBN速率,随土壤温度增加,总氨化速率(林地和灌丛)显著升高(P<0.05);随土壤含水率增加,净氨化速率(灌丛)和净硝化速率(灌丛)显著降低(P<0.05)。通过揭示天山林区土壤总氮矿化速率(总氨化速率和总硝化速率)及转化累积量对冻融过程的响应情况,本研究为天山森林土壤中氮的生物地球化学过程提供了有价值的基础数据。
基金supported by the Hundred Talents Program of the Chinese Academy of Sciences(No.29Y127D11)the National Natural Science Foundation of China(No.41271524)+1 种基金Natural Science Foundation of Gansu Province(No.1210RJDA015)Forestry Industry Research Special Funds for Public Welfare Projects(No.201104009-08)
文摘Spatial heterogeneity is an inherent characteristic of natural forest landscapes, therefore estimation of structural variability, including the collection and analyzing of field measurements, is a growing challenge for monitoring wildlife habitat di- versity and ecosystem sustainability. In this study, we investigated the combined influence of plot shape and size on the accuracy of assessment of conventional and rare structural features in two young-growth spruce-dominated forests in northwestern China. We used a series of inventory schemes and analytical approaches. Our data showed that options for sampling protocols, especially the selection of plot size considered in structural attributes measurement, dramatically af- fect the minimum number of plots required to meet a certain accuracy criteria. The degree of influence of plot shape is related to survey objectives; thus, effects of plot shape differ for evaluations of the ＂mean＂ or ＂representative＂ stand structural conditions from that for the range of habitat （in extreme values）. Results of Monte Carlo simulations suggested that plot sizes 〈0.1 ha could be the most efficient way to sample for conventional characteristics （features with relative constancy within a site, such as stem density）. Also, 0.25 ha or even larger plots may have a greater likelihood of capturing rare structural attributes （features possessing high randomness and spatial heterogeneity, such as volume of coarse woody debris） in our forest type. These findings have important implications for advisable sampling protocol （plot size and shape） to adequately capture information on forest habitat structure and diversity; such efforts must be based on a clear definition of which types are structural attributes to measure.
