全球变化背景下森林土壤动物群落对温度变化的响应机制

Temperature changing, as one of the most important aspects of the global change, is an important factor influencing the activities of soil fauna. Many researches had been conducted to reveal the effects of temperature changing on soil fauna, but the mechanisms of soil fauna responsing to temperature changing is still unclear at present. There are five climate zones from subtropics to cold on the eastern slope of Gonggashan mountains with rising elevation and the vegetation types also changed accordingly from evergreen broad-leaved forest to alpine meadow. Therefore, the the eastern slope of Gonggashan mountains is an ideal place to conduct the research on soil fauna responding to temperature change. First, three sample belts in size of 200 m × 15 m were setted in each climate zone and the investigations were conducted on the soil fauna to explore the vertical distribution patterns of soil fauna community structure and its succession rules among the different climate zones. Secondly, more than one hundred of soil columns will be excavated from the dark coniferous forest at the higher elevation and transferred to four lower elevation positions to simulate temperature increasing. Some contral measures were used to reduce the effects of unnecessary environment factors on the transferred soil columns. Both the direct and indirect effects of temperature change on the soil fauna will be analysised by monitoring the changes in the soil fauna, temperature, soil respiration and other environmental factors in the transferred soil columns and the relationships among them will also be analysised. The objects of this experiment is to disclouse the mechanisms of soil fauna responding to temperature change in the forest ecosystem. The results of this project will provide a scientific basis to predict the effects of global change on the belowground structure and function of forest ecosystems, as well as the belowground biodiversity data of the Hengduanshan Mountains.

温度升高是全球变化的核心内容之一，也是影响土壤动物活动的重要因素。目前虽有关于温度变化对土壤动物影响的报道，但关于土壤动物对温度变化的响应机制仍不清楚。本项目首先利用样带和样方相结合的方法对贡嘎山东坡从亚热带到寒带五个连续气候带上的土壤动物群落进行定位观测，研究土壤动物群落结构及多样性在不同气候带间的分布格局及演变规律；其次，利用土柱移植法把贡嘎山东坡暗针叶林内的土壤从高海拔处移植到多个低海拔处，实现自然增温，并对移植土柱采取各种控制措施以降低周围环境对移植土柱的不必要影响，通过对各移植土柱内的土壤动物、温度、呼吸速度及其它重要因子的监测，研究温度变化对土壤动物的直接及间接影响，查明森林土壤动物对温度变化的响应机制。本项目的研究结果不仅可为预测全球变化对森林生态系统地下结构和功能的影响提供科学依据，还可以丰富横断山区生物多样性基础数据。

2014至2017年间对贡嘎山东坡各垂直气候带下土壤动物以及未控制凋落物和降水（T1）、控制凋落物和降水（T2）两种增温处理和对照林地（CK）的土壤节肢动物、线虫、细菌、真菌及环境因子的4年监测，研究：（1）贡嘎山东坡土壤动物群落组成和多样性及时空分布格局；（2）森林土壤动物群落对温度变化的响应机制。主要结果：（1）贡嘎山东坡土壤节肢动物有13纲39目232科442类（属），弹尾纲占总个体数的57.07%，蜱螨亚纲占36.74 %；土壤线虫隶属于2纲、11目、70科220属，泄腺纲占全部个体数的62.38%，泄管纲占37.62%；这一结果提供了贡嘎山这一生物多样性热点地区的土壤动物及微生物多样性的详细数据，为横断山区森林生态系统功能及稳定性等评价以及热点地区生物多样性保护提供了依据；（2）查明了土壤节肢动物、螨类、跳虫、线虫的群落组成结构、密度、多样性、功能群及细菌、真菌、土壤呼吸对温度变化的响应，以及在不同处理、不同年间的差异性，揭示森林地下食物网各主要组成部分对温度变化的响应机制，为预测气候变化对森林生态系的影响奠定了坚实基础；（3）查明了T1和T2处理各移植梯度的土壤理化性质变化趋势及差异性，发现单一温度变化对土壤理化性质的影响较弱，而温度、降水、凋落物等综合因素变化对土壤理化性质影响较强；（4）分析了土壤动物、微生物、土壤呼吸等与温度、湿度、土壤理化性质等因子的关系，发现温度不是影响土壤生物群落的主要直接因子，是通过土壤理化性质等因子间接影响土壤生物，因此在必要时可以通过调控温度以外的土壤环境因子来减缓气候变暖对特定生态系统的影响；（5）比较分析了T1、T2两种增温处理下土壤生物、土壤理化性质和土壤呼吸速率等响应趋势和速度的差异性，表明不同实验条件下的增温对土壤生物及生态过程影响不同，因此在用模拟增温研究气候变化对生态系统影响时应尽可能采用接近自然真实情况的研究方法以得到客观结果。以上研究结果可为评估全球变化对森林生态系统的影响提供科学依据。