Data from: Multi-scale heterogeneity in vegetation and soil carbon in exurban residential land of southeastern Michigan, USA

Exurban residential land (one housing unit per 0.2–16.2 ha) is growing in importance as a human-dominated land use. Carbon storage in the soils and vegetation of exurban land is poorly known, as are the effects on C storage of choices made by developers and residents. We studied C storage in exurban yards in southeastern Michigan, USA, across a range of parcel sizes and different types of neighborhoods. We divided each residential parcel into ecological zones (EZ) characterized by vegetation, soil, and human behavior such as mowing, irrigation, and raking. We found a heterogeneous mixture of trees and shrubs, turfgrasses, mulched gardens, old-field vegetation, and impervious surfaces. The most extensive zone type was turfgrass with sparse woody vegetation (mean 26% of parcel area), followed by dense woody vegetation (mean 21% of parcel area). Areas of turfgrass with sparse woody vegetation had trees in larger size classes (> 50 cm dbh) than did areas of dense woody vegetation. Using aerial photointerpretation, we scaled up C storage to neighborhoods. Varying C storage by neighborhood type resulted from differences in impervious area (8–26% of parcel area) and area of dense woody vegetation (11–28%). Averaged and multiplied across areas in differing neighborhood types, exurban residential land contained 5240 ± 865 g C/m2 in vegetation, highly sensitive to large trees, and 13 800 ± 1290 g C/m2 in soils (based on a combined sampling and modeling approach). These contents are greater than for agricultural land in the region, but lower than for mature forest stands. Compared with mature forests, exurban land contained more shrubs and less downed woody debris and it had similar tree size-class distributions up to 40 cm dbh but far fewer trees in larger size classes. If the trees continue to grow, exurban residential land could sequester additional C for decades. Patterns and processes of C storage in exurban residential land were driven by land management practices that affect soil and vegetation, reflecting the choices of designers, developers, and residents. This study provides an example of human-mediated C storage in a coupled human–natural system.

远郊住宅用地（每0.2–16.2公顷配置1套住宅单元）作为一种人类主导的土地利用类型，其重要性与日俱增。目前，远郊土地的土壤与植被碳储量，以及开发商与居民的决策对碳储量的影响，均尚未得到充分研究。本研究以美国密歇根州东南部的远郊庭院为研究对象，涵盖了不同地块规模与多种社区类型。我们将每个住宅地块划分为基于植被、土壤以及修剪草坪、灌溉、耙地等人类活动特征定义的生态分区（Ecological Zones, EZ）。研究区域内存在异质性极强的景观组分组合，包括乔灌群落、草坪、覆盖地膜的菜园、撂荒地植被以及不透水地表。占比最高的生态分区类型为稀木草坪（平均占地块面积的26%），其次为密生乔灌群落（平均占比21%）。稀木草坪区域内的树木径级（>50 cm 胸径（diameter at breast height, DBH））显著大于密生乔灌群落区域。通过航空照片解译，我们将碳储量的测算尺度扩展至社区层面。不同社区类型的碳储量差异，源于不透水地表占比（地块面积的8%–26%）与密生乔灌群落面积（11%–28%）的不同。对不同社区类型的区域进行平均与尺度放大后，远郊住宅用地的植被碳储量为5240 ± 865 g C/m²，其储量对大型树木极为敏感；土壤碳储量为13800 ± 1290 g C/m²（该结果基于采样与建模相结合的方法）。该碳储量水平高于区域内的农田，但低于成熟林分。与成熟林相比，远郊土地的灌丛占比更高，但枯倒木残体更少；在40 cm胸径以下的树木径级分布与成熟林相近，但大径级树木的占比显著更低。若树木持续生长，远郊住宅用地可在数十年内持续固存更多碳。远郊住宅用地的碳储量格局与过程，由影响土壤与植被的土地管理实践所驱动，这反映了规划师、开发商与居民的决策选择。本研究为耦合人文-自然系统中人类介导的碳储量研究提供了范例。