荒漠藓类植物齿肋赤藓对4年积雪深度变化的生理生化响应

Ecophysiological and biochemical responses of desert moss Syntrichia caninervis to changes of snow depth in four years

冬季降雪作为古尔班通古特沙漠最主要的降水形式,在荒漠生物土壤结皮的稳定和发育发挥重要作用。全球的持续变暖和极端气候事件的频繁发生导致荒漠冬季的积雪格局发生重大变化。荒漠藓类植物作为荒漠重要地被类型生物土壤结皮的重要组成成分,在生理生化层面将如何响应长期的积雪深度变化还不清楚。因此,通过野外设置去除积雪(-S)、自然积雪(S)、2倍积雪(2S)和3倍积雪(3S)4个积雪梯度,探讨经历4年积雪深度变化下齿肋赤藓(Syntrichia caninervis)的生理生化特征。结果表明,积雪深度变化显著影响了齿肋赤藓的植株含水量、最大光化学量子产量(F_(v)/F_(m))、实际光化学效率(Y(II))、渗透调节物质含量和抗氧化酶活性。与去除积雪处理相比,随着积雪深度的增加,齿肋赤藓的植株含水量、F_(v)/F_(m)和Y(II)呈现增加趋势,而植株内的游离脯氨酸、可溶性蛋白、可溶性糖、丙二醛(MDA)含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)及过氧化氢酶(CAT)活性呈现降低趋势。相关性分析显示,齿肋赤藓的F_(v)/F_(m)和Y(II)与土壤温度和植株含水量呈显著正相关,而可溶性蛋白、可溶性糖、MDA含量及SOD、POD和CAT活性与土壤温度和植株含水量呈显著的负相关。值得注意的是,与自然积雪相比,4年3倍积雪增加处理显著降低了齿肋赤藓的Y(II),增加了MDA含量。这说明积雪在一定程度上为齿肋赤藓创造了良好的生存环境,降低了齿肋赤藓的干旱和冷胁迫程度,但长期大量的积雪增加和长期减雪均会对齿肋赤藓的生长造成负面影响。

Winter snowfall,as the main form of precipitation in Gurbantunggut Desert,plays an important role in the stability and development of biological soil crust(BSCs).The pattern of snow cover in winter has changed greatly due to continuous global warming and frequent occurrence of extreme climate events.As an important component of soil crusts,it is not clear how desert mosses respond to long-term snow depth changes at physiological and biochemical levels.In this study,four snow gradients,including snow removal(-S),ambient snow(S),double snow(2S)and triple snow(3S)were set up in the field,to investigate the physiological and biochemical characteristics of Syntrichia caninervis after four years of snow depth change.The results showed that the change of snow depth significantly affected plant water content,the maximum photochemical efficiency(F_(v)/F_(m)),the effective photochemical quantum yield of PSII(Y(II)),osmotic regulation substance content and antioxidant enzyme activity.Compared with the treatment of removing snow,the water content,F_(v)/F_(m)and Y(II)of Syntrichia caninervis increased with the increase of snow depth,however,the contents of free proline,soluble protein,soluble sugar,malondialdehyde(MDA)and activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)showed a decreasing trend.Correlation analysis showed that F_(v)/F_(m)and Y(II)of Syntrichia caninervis were significantly positively correlated with soil temperature and plant water content,while soluble protein,soluble sugar,MDA content,SOD,POD and CAT activities were significantly negatively correlated with soil temperature and plant water content.Notably,3S increase in snow cover for 4-year have significantly decreased Y(II)and increased MDA content of Syntrichia caninervis compared with natural snow cover.These results indicated that snow cover has created a suitable habitat for Syntrichia caninervis,and reduced the degree of drought and cold stress of Syntrichia caninervis.However,the growth of the Syntrichia caninervis would be negatively affected by both long-term snow accumulation and long-term snow reduction.