Moss-biocrusts strongly decrease soil surface albedo, altering land-surface energy balance in a dryland ecosystem
Moss-biocrusts strongly decrease soil surface albedo, altering land-surface energy balance in a dryland ecosystem
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苔藓生物结皮强烈降低土壤表面反照率，改变旱地生态系统的地表能量平衡
DOI：
10.1016/j.scitotenv.2020.140425
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发表时间：
2020
影响因子：
9.8
通讯作者：
Matthew A. Bowker
中科院分区：
文献类型：
--
作者：
Bo Xiao;Matthew A. Bowker
陆地表面辐射测量太阳辐射被吸收或反射的程度，因此可以对全球气候趋势，当地天气现象和生物过程产生重大影响。作为旱地广泛的生物覆盖物，生物结壳覆盖了大量的陆地表面，但其对地表水分和能量平衡的潜在影响却没有得到充分的记录，其时间动态几乎是未知的。连续两年对苔藓生物结皮覆盖土壤和倮地的地表水分、地表能量平衡、温度和湿度进行了观测，并对两种土地覆盖类型的地表颜色和粗糙度进行了测量。结果表明，生物结皮的表层土壤湿度比裸土低43.4%，这是由于生物结皮层的黑暗度（43.7%）和粗糙度（90.4%）增加以及含水量（20.7%）增加所致。随着时间的推移，生物结皮的蒸腾速率与表层土壤温度或水分呈线性负相关，导致生物结皮的蒸腾速率在夏季较低，而在其他季节较高。由于生物结皮减少了光能吸收，使土壤短波辐射减少了44.8%，从而使净短波辐射增加了11.4%，净全波太阳辐射增加了22.9%，但生物结皮增加的能量吸收并不一定使土壤温度增加;相反，土壤温度在干燥条件下增加了9.3 °C，但在潮湿条件下下降了11.4 °C，导致净冷却。这表明，生物结皮覆盖的土壤的温度状况不仅取决于水分，但也通过修改土壤的热性质的生物结皮。由于生物结壳对土地利用高度敏感，因此，人类活动影响气候和天气的方式之一可能是改变生物量和能量平衡。
Land surface albedo measures the degree to which the sun's radiation is absorbed or reflected, and thus can be highly influential in global climate trends, local weather phenomena, and biological processes. As an extensive living cover in drylands, biocrusts cover substantial land surface but their potential influences on surface albedo and energy balance are underdocumented, and its temporal dynamic is virtually unknown. We continuously measured the surface albedo, land-surface energy balance, temperature and moisture of moss-biocrust covered soil and bare soil for two years, and measured the surface color and roughness of the two land cover types. Our results showed that the surface albedo of the biocrusts was 43.4% lower than that of the bare soil, due to the increased darkness (43.7%) and roughness (90.4%) together with increased moisture (20.7%) of the biocrust layer. Through time, the albedo of the biocrusts were negatively and linearly related with surface soil temperature or moisture, which resulted in lower albedo in summer and higher albedo in other seasons. As a result of decreased albedo, biocrusts decreased outgoing short-wave radiation by 44.8% in comparison to the bare soil, and consequently they increased net short-wave radiation by 11.4% and net all-wave solar radiation by 22.9% However, the increased energy absorption by the biocrusts did not consistently increase soil temperature; instead, soil temperature increased by up to 9.3 °C under dry conditions but decreased by as much as 11.4 °C under wet conditions, resulting in a net cooling. This indicates that the temperature regimes of the biocrust-covered soil were not determined only by albedo, but also by modification of soil thermal properties by biocrusts. Because biocrusts are highly responsive to land use, it appears that altered albedo and energy balance may be one of the ways in which human activity can impact climate and weather.