Van Stan John T, Gordon Dennis A
Geology and Geography, Georgia Southern University, Statesboro, GA, United States.
Front Plant Sci. 2018 Feb 27;9:248. doi: 10.3389/fpls.2018.00248. eCollection 2018.
Stemflow, a precipitation and solute supply to soils near tree stems, can play a wide array of roles in ecosystem functioning. However, stemflow's ecohydrological functions have been primarily studied in forests with voluminous stemflow because resource subsidy is currently considered stemflow's only impact on near-stem soils. This common assumption ignores controls that stemflow generation may exert via resource limitation (when stemflow < open rainfall and near-stem throughfall is negligible). We reviewed selected literature across numerous forests to evaluate the predominance of stemflow as a potential resource limitation to near-stem soils and characterized the concentrated, but meager, solute flux from low stemflow generators. Global observations of stemflow were highly skewed (skewness = 4.6) and leptokurtic (kurtosis = 28.8), where 69% of observations were ≤2% of rainfall. Stemflow ≤ 2% of rainfall is 10-100 times more chemically enriched than open rainfall, yet low volumes result in negligible solute fluxes (under 1 g m y). Reduced stemflow may be the global and regional norm, creating persistently dry near-stem soils that receive infrequent, salty, and paltry precipitation flux if throughfall is also low. Ignoring stemflow because it results in scarcity likely limits our understanding of ecosystem functioning as resource limitations alter the fate of soil nutrients, energy flows, and spatial patterning of biogeochemical processes.
茎流作为树干附近土壤的降水和溶质供应，在生态系统功能中可发挥多种作用。然而，茎流的生态水文功能主要在茎流量大的森林中得到研究，因为目前资源补贴被认为是茎流对近茎土壤的唯一影响。这种普遍假设忽略了茎流产生可能通过资源限制施加的控制作用（当茎流＜开阔降雨且近茎穿透雨可忽略不计时）。我们回顾了众多森林的相关文献，以评估茎流作为近茎土壤潜在资源限制的主导地位，并描述了低茎流产生者集中但稀少的溶质通量。全球范围内对茎流的观测高度偏态（偏度 = 4.6）且峰态较高（峰度 = 28.8），其中69%的观测值≤降雨量的2%。茎流≤降雨量的2%时，其化学富集程度比开阔降雨高10 - 100倍，但量少导致溶质通量可忽略不计（低于1 g m² y⁻¹）。茎流减少可能是全球和区域的常态，若穿透雨也少，就会造成近茎土壤持续干旱，接受的降水通量稀少、含盐且微不足道。因茎流导致资源稀缺而忽视它，可能会限制我们对生态系统功能的理解，因为资源限制会改变土壤养分的命运、能量流动以及生物地球化学过程的空间格局。
