本地草坪的生态优势与可持续景观设计

"So appropriate for the Southwest, where water is so scarce, but it provides lessons for us all. The key is aesthetics. Natives and low-water plants can be more beautiful than lawns."—2013 Professional Awards Jury

它极为适合西南地区，那里水资源较少。但它值得所有人学习。这个项目的关键在于它体现的美学价值。当地耐旱植被比草坪景观更美。

——2013专业奖项评委

The Lawn is Dead – Long Live the Lawn

By Lady Bird Johnson Wildflower Center / University of Texas at Austin

草坪在现代城市景观中被广泛应用，在为城市增加美观的同时其对水源、肥料、农药和割草的高度需求也使这种景观饱受争议。因此我们对一片由本地草坪草种衍生出来的混合型草坪进行了研究。结果表明这种草坪生长速度更快，具有较高的叶片密度，更不容易长出它杂草而且不需要频繁的割草。如果我们将这种生态草坪设计方法进行推广，它将会对所有草坪景观的生态足迹产生深远的影响。

Turf is widely used in urban landscapes, but is frequently criticized due to high demand for water, fertilizer, pesticides and mowing. This research assessed a turf mix derived from regionally-native turfgrass species and determined that it established faster, had higher leaf density, fewer weeds and required less mowing than a common non-native turf. A similar ecological design approach to turf design elsewhere would have a profound effect on the environmental footprint of all turf landscapes.

这些经过筛选的结构相似的地域性商业草坪草种（同样的颜色、高度、叶片宽度等）广泛分布于北美地区。这表明拥有一些可替换草种的相似草种混合型草坪同样可以适用于其它地区。

Selected for structural similarity to commercial turfgrass (same color, height, leaf blade width etc.) these native grass species have a geographic range across North America. This suggests similar mixes with some species substitutions would be suitable for other regions.

本地具有较深根系的草皮草具有多种生态优点：储存二氧化碳，加大水分渗透（防洪蓄水/改善水质），保持水土并增加栖息地面积。这些被测试的草种都是寄生植物并且能为许多种蝴蝶和蛾子提供食物。

Native turf grasses, with deeper root systems, have many ecological benefits: sequestering CO2, increasing water infiltration (flood mitigation | improving water quality), reducing erosion, and providing habitat. These tested grasses are host plants and food sources for several species of butterfly and moth.

经过长期的火灾和放牧的洗礼，本地草种已经进化到能将大部分的生物能量储存于地下。和地上生物能量不同，湿式系统（泥炭地和湿地）草地具有最高密度的地下碳储存量，而且它们能够将碳储存达1000,000年之久。

Evolved with fire and grazing, native grasses keep most biomass below ground. After wet systems (Peatlands and Wetlands), Grasslands have the highest density of below ground carbon, which, unlike above ground biomass, can sequester carbon for 100,000s of years.

根据行业标准，普通狗牙根草需要修剪的频率远远高于本地草种。如果不及时修剪，狗牙根草就会长出大量分支，遮住下面的分蘖并使其褪色。割去“头皮”部分就会露出下面难看的褐色分蘖。

Industry standard, common Bermudagrass must be mowed at a higher frequency than the native turf. Left unmown, Bermudagrass branches aerially, shading the tillers below so they become discolored. Mowing ‘scalps’ the green canopy revealing unsightly brown tillers below.

研究表明混合草皮的草种数量越多，草坪的叶片密度就越大，也就越难长出杂草。

This research found the more grass species included in the turf mix the greater the leaf density and the fewer the number of weeds.

单一草种的“生态位体积”较窄并且容易被其它不同生态位体积的杂草侵袭。相反，由本地草种组成的混合式草坪不仅具有相同的审美外观，具有更大的生态位体积并且不容易被杂草侵袭。

A monoculture has a narrow ‘niche volume’ and is open to invasion by weeds with different niche dimensions. By contrast, a mix of native grasses, although aesthetically identical, fills a greater volume of niche space and is resilient to invasion.

该研究把由七种本地草种组成的草坪与本地最常见的商业草坪进行了对比。

我们建立了许多小块试验田来检验杂草入侵、灌溉和压实效果。

The study examined the performance of mixes of seven native grasses against the most commonly used lawn grass in the region. Plots were tested for establishment, weed invasion irrigation and compaction.

本研究是开放式的，它检验了混合草种草坪在绿色屋顶上的应用以及多草种草皮在园艺、生态和可持续性上的良好表现。

The study, open to public demonstration, examines the application of the turf mix for green roofs and the addition of more species to increase horticultural, ecological and sustainable performance.

无论怎样修剪，本地草种草皮都比传统的非本地单一草种草皮质地更加柔软。

Mowed short or long, the native turf has a much softer texture than conventional, non-native monocultures.

本地草种草皮也被应用到了校园景观设计中。在达拉斯州的乔治布什总统中心就有几英亩大的这种草坪。这些没人修剪的草坪具有很好的可持续性，带有穗子的草坪成了一道亮丽的风景。

The native turf mix is also being used on campuses. Several acres of this turf have been installed at the George W Bush Presidential Center in Dallas, where left unmowed, the grasses form a sustainable turf with attractive seed heads.

Project NarrativeProblem

Turfgrasses are a dominant urban and sub-urban landscape type contributing to roadsides, parks, campuses, golf courses, utility rights-of-way, and residential lawns. These landscapes, however, are justifiably villainized due to their high demand for water, fertilizer, pesticides and mowing.

Fifty million acres of turfgrasses in both commercial and residential applications represent the primary irrigated crop in the United States, absorbing up between 30% and 60% of potable urban water. Lawns alone annually consume 67 million pounds of pesticides, 70 million tons of fertilizer, as well as 300 million gallons of gasoline producing 5% of the nation’s air pollutants. The resource dependence of this landscape type over the last 40 years has been the direct result of the development of cheap fertilizer and pesticides, breeding of nutrient-dependent grasses and theavailability of water. The result is an industrial landscape that has become neither environmentally responsible nor economically viable.

Solution

Given the highly desirable aesthetic of this landscape type, we questioned the suitability of species selection and performance of the conventional monocultural non-native turfgrasses. Could a suite of naturally occurring, coexisting, turfgrass species with identical leaf appearance, not only meetthe aesthetic and performance expectations, but also, result in the reduction of environmental costs in terms of resource consumption and maintenance requirements? So a series of replicated test plots were designed to assess and compare establishment rates, leaf density, compaction disturbance, and weed infestation of a standard non-native turfgrass, against naturally occurring suites of regionally-native seed mixes. The data demonstrated that native turfgrasses established faster, had higher leaf density, fewer weeds and required less mowing than the conventionally turfgrass. This supports the hypothesis that ecologically-stable native turfgrass communities adapted to the low nutrient soils and regional climatic conditions are better, or at least, as-well suited, as commercial turfgrass species. This has beneficial implications not only from the perspective of lower maintenance needs and reduced environmental risk, but also for biodiversity value, resource requirements and carbon footprint of all turfgrass landscapes.

Conclusion and Next Steps

This turfgrass mix is already available commercially and is being implemented on residential and large commercial landscapes. But this research does not stop here. We are currently proposing to the network of public gardens around the nation to replicate this technology regionally. The adoption of similar ecological design protocols to turfgrass elsewhere could have a significant positive effect on sustainability and environmental footprint of all urban landscapes.

This research project presentation demonstrates:Distributions and characteristics of selected species

Benefits of an ecologically designed turf

Disadvantage of the commonly-used non-native turfgrass monoculture

Weed resistance of the multi-species turf and the underling ecological theory

Large scale application examples

Residential application examples

Public outreach （via : asla