黄土高原地区森林生态系统地下生物量影响因素

根系将土壤和大气相连与植物体共同影响生态系统的碳循环，同时根系也是森林生态系统土壤碳库的重要来源。研究表明森林地下生物量受生物因素和非生物因素影响，因此研究各因素对根系生物量的影响对精确估算土壤碳库至关重要。基于我国相关部门的观测及调查数据，通过标准化计算和统计分析来量化各因素对黄土高原地区地下生物量的影响。结果表明：黄土高原森林生态系统地下生物量主要分布在11.99-27.46 Mg/hm²之间；非生物因素对地下生物量起主导作用，其中降雨量和地形影响最为显著；不同土壤类型地下生物量表现出：棕壤 > 褐土 > 岩性土；不同森林类型地下生物量大小为：针叶林 > 针阔叶混交林 > 落叶阔叶林；不同地形地下生物量由大到小为：丘陵、山地 > 高原、平原；地下生物量在坡位上的分布大小为：坡麓 > 上、中、下三个坡位 > 平地；人类活动和动物活动干扰对地下生物量的影响没有显著差异。另外，在分析中发现若影响因素中含经纬度，非生物和生物因素对地下生物量的影响程度分别为68.9%和31.1%；若影响因素中不含经纬度，非生物和生物因素对地下生物量的影响程度分别为81.1%和18.9%，说明经纬度与其他因素存在很强的相关性，并严重影响着生物因素和非生物因素对森林生态系统地下生物量的比重。研究结果对地下生物量的估测有一定的意义，可以为森林植被如何通过根系适应环境的研究提供参考，为植被恢复、森林经营管理及地下部分碳循环的研究提供依据。

Factor analysis of underground biomass in forest ecosystem on the Loess Plateau

Root which connects soil and atmosphere and plant have a combined effect on the carbon cycle in the ecosystem. Meanwhile, root is also an important source of soil carbon pool in forest ecosystem. Previous studies showed that the forest underground biomass was affected by biological factors and abiotic factors, thus it is of great importance to determine the effect of various factors on root biomass for accurate estimation of soil carbon pool. Based on the observation and survey data of relevant departments in China, standardized calculation and statistical analysis methods were used to quantify the effect of various factors on the underground biomass in the Loess Plateau. There are 15 factors in this study, among which the abiotic factors are longitude, latitude, annual rainfall, annual mean temperature, altitude, topography, slope direction, slope position, slope angle and soil type. The other five factors are biotic factors, which are forest type, forest origin, forest age, animal activities and human activities. The results showed that the underground biomass in forest ecosystem in the Loess Plateau ranged from 11.99 Mg/hm² to 27.46 Mg/hm². Abiotic factors had dominant influence in the underground biomass, particularly for the rainfall and topography. The order for underground biomass was brown > cinnamon > lithologic soil in different soil types, coniferous > coniferous broad-leaved mixed > deciduous broad-leaved forest in different forest types, hillly and mountainous > plateau and plain terrain in different topography respectively. The distribution of underground biomass on the slope was:the foot of mountain slopes > upper, middle and lower slope > flat land. There was no significant difference between human activities and animal activities. We found that the proportion of biotic and abiotic factors on the underground biomass was severely affected by longitude and latitude. It was 68.9% and 31.1% with longitude and latitude factors, otherwise it was 81.1% and 18.9%, respectively. The results indicated that latitude and longitude had a strong correlation with other factors. In addition, controlling a single factor explained the influence of the other factors on the underground biomass. For example, the main factors determining the underground biomass in humid area were annual temperature (19%) and slope position (19%). Our study could have implications for the estimation of underground biomass, which could provide a reference for plantation root adaptation to the environment, and put forward the theoretical basis for the study of vegetation restoration, forest management and underground carbon cycle.