A 3-dimensional model of Pinus edulis and Juniperus monosperma root distributions in New Mexico: implications for soil water dynamics
A 3-dimensional model of Pinus edulis and Juniperus monosperma root distributions in New Mexico: implications for soil water dynamics
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DOI：
10.1007/s11104-020-04446-y
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发表时间：
2020-04-11
期刊：
影响因子：
4.9
通讯作者：
McIntire，C. D.
中科院分区：
文献类型：
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作者：
Schwinning，S.;Litvak，M. E.;McIntire，C. D.
目的(1)建立仅以树种、大小和位置为输入的青柏林地三维根系分布模型。(2)解释土壤水分与根系分布的两年时间序列。Sarg.)新墨西哥州的林地。从3条10米长、1.5米深的沟渠壁上切下720块土块(30 cm × 10 cm × 10 cm)，提取根。根按树种和径级进行分类。建立了直径为5 mm的≤根干重的分布模型。连续2年对树丛和林窗下土壤水分和水势进行了测定。结果皮尼翁的根干质量是刺柏的2倍，与树冠投影面积的比例相近。与树丛相比，林窗下土壤中的根密度低约50%，树种比在树丛和林隙之间没有显着差异。与杜松相比，皮尼翁根系密度随土层深度和距树干距离的增加而下降得更快。60-80 cm土层坚硬的钙质层对该深度本已较低的根系密度没有明显影响。总体而言，模型解释了采样土块尺度上根系密度空间变异的66%(piñon)和54%(Juniper)。在8个月的干旱期间，土壤水分在根系密度较高的地区下降得更快：浅层土壤和树丛下。这在林窗下的深层土壤中留下了可供植物利用的土壤水分储备。结论这些开阔林地根系密度的水平变化是可预测的，是植物-土壤动态相互作用的重要组成部分。在干湿条件下，树丛和林隙下土壤水分含量有很大不同。
Aims(1) To develop a 3D root distribution model for piñon-juniper woodland using only tree species, sizes and locations as input. (2) To interpret a two-year time series of soil moisture relative to root distributions.MethodsThe study was conducted in a piñon (Pinus edulis(Englem.)) -juniper (Juniperus monosperma(Englem.) Sarg.) woodland in New Mexico. We extracted roots from 720 soil blocks (30 cm × 10 cm × 10 cm) cut from the walls of three 10-m long and 1.5-m deep trenches. Roots were sorted by species and diameter class. Distribution models were developed for the dry weight of roots ≤5 mm in diameter. Soil water content and water potentials were measured in soil profiles under tree cluster and canopy gaps for 2 years, including a protracted dry-down period.ResultsPiñon had twice the root dry mass of juniper, similar to the ratio of canopy projection areas. Root densities were ca. 50% lower in soils under canopy gaps compared to tree clusters and the species ratio did not significantly differ between clusters and gaps. Piñon root density declined faster with soil depth and distance from the stem compared to juniper. A hard caliche layer at 60–80 cm soil depth had no apparent effect on the already low root density at that depth. Overall, the models explained 66% (piñon) and 54% (juniper) of the spatial variation in root density at the scale of sampled soil blocks. During an 8-month dry period, soil moisture declined faster in regions of higher root density: in shallow soil and under tree clusters. This left a reserve of plant-available soil water in the deep soil under canopy gaps.ConclusionsHorizontal variation in root density in these open woodlands is predictable and an important component of the dynamic interactions between plant and soil. Under wet and dry conditions, soil water content is substantially different under tree clusters and canopy gaps.