休斯顿植物园与自然中心荒废林区生态修复工程

“项目团队着实对荒废地带大量树种的死亡原因做了十分详尽的研究与分析，并对荒废林区的生态修复制定了具体而有效的规划方案，以确保林区树种的长期、健康生长态势。” —2014ASLA分析与规划专业奖评语 “They really studied the causes of the massive tree canopy mortality rate, creating a plan to renew the beautifully forested area that was devastated and retain the quality of the trees over time.”- 2014 Awards Jury


项目概述

休斯顿植物园与自然中心位于当地纪念公园林区内，占地155英亩（约63公顷），由于长期受到干旱、飓风等恶劣气候的影响，其生态环境遭受严重破坏。对于这一系列自然林区进行合理的生态修复性规划已经势在必行，而规划方案的重点在于项目场地固有自然和文化遗产的具实评估、气候变化影响的具体分析，以及广大利益相关者的参与机制。该项目规划有力地促进了植物园生态环境的未来健康发展，同时也为其它地区的同类环境修复项目提供相应参照。

项目描述

项目挑战
休斯顿植物园与自然中心位于布法罗河口，占地155英亩（约63公顷），是当地重要的林地资源，也是本土动植物的天然生境，同时还是休斯顿的重点环境教育基地。植物园所在的当地大型纪念公园林区，占地1500英亩（约607公顷），由Hare & Hare景观设计与规划事务所于1925年设计营造。20世纪50年代，该林区初具规模，各类天然植物长势良好，形成系统化的理想林区自然生境。然而，近年来，受到干旱、飓风等恶劣气候的影响，林区内48%的树种面临死亡威胁，加之大量外来物种的入侵，生态环境遭受严重破坏。而该项目总体规划的主要难点在于将该林区固有的生态与文化历史与相应的现代需求相融合，进而营造出一处灵活有效且能够迎合社会需求的修复性林区环境。

“为社会各年龄层的人们提供良好的自然生态环境教育基地是该植物园与自然中心修复项目的主要使命，此外，还应对植物园进行有效的环境保护与环境改善，以为本土动植物营造出理想的天然生境。”

社会反响
一个项目总体规划方案的具体制定，其关键在于初始阶段社会各界对项目价值及未来愿景的深入理解。通过一系列的会议调研形式，让社会各公共及私人团队和个人广泛参与其中，使得包括教师、林区住户、植物园员工及董事会成员、休斯敦市政工作人员、纪念公园管理协会董事会成员、林区建设捐助者及其他各利益相关者都有均等的机会为项目规划献计献策。这样的广泛性社会调研活动为社会各界利益相关者成功搭建起良好的对话式互动平台，也为所有的参与者们深入了解项目的社会价值提供了宝贵的机会。调研活动中，利益相关者们为项目规划确立了两大主要目标——实现林区景观的多样性、实现规划区域与野生林地的生态平衡。针对大众普遍关注的树木大量死亡问题，景观设计师们必须妥善应对，既要有效修复林区原有的特色自然环境，又要使得相应的规划方案能够适应生态系统不断变化的现实情况。设计团队首先对林区的周边环境进行了有效修复与整合，使其对不断变化中的核心多样生态系统形成有力的外围支撑与保护。

“廊道”设计优先可选性方案迎合了利益相关者所确立的相应目标，在充分尊重项目场地原始文化和生态环境的前提下，结合其他相关辅助性规划活动，对植物园的天然生境进行有效修复。最终的综合性规划方案为营造一处世界级的天然景观林区奠定了坚实的基础，林区环境修复后，将吸引大批市民和观光者前来开展各类环境保护教育活动，并广泛传播植物园林区存在和修复的重要意义，增强大众的林区保护意识。

生态论证
景观设计团队充分利用论证法，对项目场地的土壤类型、排水方式、树冠长势、植物多样性等诸多方面进行了广泛而深入的分析，并研究其特殊的地质条件及相应的基本情况，试图寻找出导致大量树种死亡的根本原因。由科学专家和设计师共同组成的跨领域协作团队还通过地理信息系统（GIS）进行相应的场地分析与研究。分析结果表明，树种死亡高发区（死亡率高达70%以上）往往都是富含粉质粘土壤并存在大量凹凸地形的草原景观区，这样的地形条件易于导致微生态环境的滋生。凹陷地形中的树种，根系生长层较浅，易于造成水土流失，不利于树种吸收土壤水分和养分，树木生长其中，长期缺乏水分和养分的供给，因此，旱季就成了树木死亡的高发期。奇怪的是，在凸现地形中的树种，根系生长层反而较深，旱季中这些树种的存活率就相对高些。

这种生态格局是由近年的气候变化形成的，同时也是多样化生态全新景观镶嵌体产生的具体体现。环境叠置的形成过程有助于确定不同景观类型的最佳生存条件。例如，目前林区内的草原地形仅占2%，然而却有49%的场地，其地形特征适合草原开发。这一研究成果有利于项目的决策者对整个项目规划进行必要的方向性调整，为林区适当增加草原地块面积，以使修复后的林区景观整体更能灵活应对未来的环境变化。各特色景观区的全新组合，形成了项目场地生态交错带上极其丰富的生态多样性。草原、热带牧区、沼泽区、阔叶林区以及滨水林区都不再是静态、孤立的生态空间环境，而是形成林区生态互联系统中的灵活分枝。设计团队通过不同类别林地具体而有效的灵活迁徙，营造出更为合理、科学的林区生态，而新增植物也都根据特定的土壤和水文条件进行合理种植。

整体平衡
总体规划方案中还对相应的林区基础设施进行了合理改进，以为人们提供更为便捷的林区观光条件，使观光者们拥有更为多样化的生态环境体验和更加愉悦的观光旅程，令他们对林区的全新生态系统有更为深入的了解。植物园目前的年游客接待量为80万人次，是休斯顿地区宝贵的生态教育基地和天然开放空间资源。各学校团体都会定期组织相应的参观活动，以加强对学生的自然环境教育，林区内还频繁出现现场成人环境教育学习班。此外，总体规划中也对林区内相应的营地活动服务区进行了有效拓展，同时也考虑人流量因素，通过相关的规划措施在指定观光区和非指定性自然林区实现观光人流的平衡分布，而这两大区域内的合理人流量衡定标准则取决于各自小型观赏性植物园数量的多少。市政相关决策者对于这一总体规划系列建议书的有力批注与支持，也从很大程度上推动了相关细节规划方案的施行。

林区内85%的区域依然作为自然生态保护区得以保留，而游客观光区的核心区域内将铺筑一系列风格各异的步道系统。目前，在现有各特色景观区中总长达20,150英尺（约6.1公里）道路建设中，已经拥有6种风格不同的林区步道，为游人的观光旅程平添了许多乐趣。规划方案中，还依据各全新及修复型特色景观区和体验区的相应分布，开辟出11条教育性游园步道。而整个纪念公林区的所有步道总长增加到39,061英尺（约12公里），同比增长94％，让游客们在游览植物园的同时，也能顺道游览并体验更为广袤的休斯顿生态林区。

大规模的基础设施扩增建设加快了林区内非透水性平坦地块的改造性建设步伐，同时，对当地的水文和水质改善也起到了积极的推动作用，有利于促进布法罗河的水质改善。为了减缓新增基础设施对于当地生态环境的潜在负面影响，总体规划中还对现有的沥青停车区进行拆迁处理，并规划建造相应的透水性停车场设施，此外，还将稳定性较强的本土草坪地被区也划入作为停车区，且对非透水性地块施行有效的雨水收集。该项目迎合了当地具体地形需求，综合规划建造了全新的建筑、步道及其他内置性功能设施，以有效减缓林区侵蚀，确保林区水质。湿地池塘的建造和大量植栽的种植，有效过滤并清洁了林区水源，增加植物园的生境多样性。

渐进修复
作为对生态危机的有力回应，该项目总体规划着重发掘林地生态系统自我修复能力，并力图成为德克萨斯州东南部及其他持续干旱地区的生态修复典范。在该项目中，与一系列生态系统修复性原始设计同样重要的是相应管理体制的制定，便于对生态性能的定期评估和潜在不确定性因素的定期处理。通过一系列综合性管理机制的确立及专业化志愿者团队的建立，总体规划中规定了相应的策略性干预措施，以有效运作全新的动态化生态环境。树种的水土流失情况将得以有效缓解，并有效确保大规模植栽区的充足水分，为因干旱而退化的林地土壤进行重要的有机物回流补给。入侵性植物灌木丛将被移除，并加强林地核心区域和其它本土植栽的养护和管理。志愿者们将对全新开辟的植栽区进行持续性矩阵式种植。草原与热带牧区中的一系列划割地将进行定期播种，并通过一年一度的割草或控制性燃烧，使这些草种得以有效再生。林区的策略管理趋向系统化的弹性动态化发展机制，实现植物园的真正使命：营造一系列的自然生境和相互关联的动态林地系统，以有力取代原先简单而不科学的树种整合。


Image by: Design Workshop, Inc.


休斯顿植物园位于美国休斯顿的布法罗河口，地处墨西哥湾沿岸平原生态区内，在支流洼地密布的茂林峡谷中衬托出邻近草原的广袤平坦
Located along Buffalo Bayou in Houston, the Arboretum lies within the Gulf Coastal Plains ecoregion, supporting vast flat prairies that abut wooded ravines associated with bayous and depressions.
Image by: Design Workshop, Inc.


受飓风艾克及近期发生的历史性旱灾等自然灾害的影响，植物园的景观维护岌岌可危。该项目规划方案旨在打造一个更具生态多样性和自我修复性的景观林区，以更好地应对未来发生的自然灾害
Impacted by the natural disaster of Hurricane Ike and a recent historical drought, the Arboretum represents a landscape in crisis. The proposed design is a more ecologically diverse and resilient landscape, designed to better handle future disturbance.
Image by: 214-02 Art Work of Houston, Texas: Published in Twelve Parts: 03-Page3.1904


相应的取证分析表明了大量树种死亡的真正原因。该地多为粉质粘土壤，普遍排水不良——这是草原环境的典型状况
Forensic analysis of the site explained significant canopy loss. Poorly drained areas with silty clay loam soils – conditions more representative of prairie environments – were widespread on the site.
Image by: Design Workshop, Inc.


利用基线清单数据确定每个潜在景观类型的生态适应性，从而形成活力十足的多样化景观格局，真正反映出植物园的区域生态环境
Using baseline inventory data, ecological suitability was determined for each potential landscape type. The result is a diverse and resilient mosaic that is an authentic representation of the Arboretum’s regional ecological context.
Image by: Design Workshop, Inc.



新规划方案提出了渐进式实施策略，回收营养物质并招募志愿者，以修复当地生态，教导当地社区对本土景观进行长期管理
The new plan sets forth an evolutionary implementation strategy, recycling nutrients and employing volunteers in order to restore the site and educate the community on long-term management of native landscapes.
Image by: Design Workshop, Inc.


植物园的修复工作将从受损景观的选择性清理着手。其景观将在今后40年内得以再生，成为更具可持续性的生态系统
Restoration of the Arboretum will be a process that begins with selective clearing of the disturbed landscape. Over the next 40 years, the landscape will be regenerated to become a more sustainable ecosystem.
Image by: Design Workshop, Inc.


改善的林地及修复的本土生态系统（如草原和热带牧场）构成了一系列景观特色区，教育受众保护环境，同时丰富游人体验
Enhanced woodland habitat and restored native ecologies, such as prairie and savannah, create a series of landscape character zones that educate users and enrich visitor experience.
Image by: Design Workshop, Inc.


1. 根据微地形、水文及土壤的具体要求营建苗圃
2. 利用植物群落的多样性扩大野生动植物生境规模
3. 在群落交错带边缘对入侵物种进行有效管理
1. Establish Plantings based upon specifics of micro—topography, hydrology & soil requirements.
2. Increase wildlife habitat through a diversity of flora.
3. Manage invasive species at ecotone edges.
Image by: Design Workshop, Inc.


1. 利用挑高的木板桥保护脆弱的栖息地及排水格局
2. 保留枯立木，增加植栽量，以便野生动植物生境的良好发展
3. 增强林下植被层培植
1. Protect sensitive habitats and drainage patterns with elevated boardwalks.
2. Retain snag trees and promote plantings for wildlife habitat.
3. Develop vegetative layers of woodland understory.
Image by: Design Workshop, Inc.


1. 修复并稳固河岸廊道
2. 集约化原生植栽为游人提供了与众不同的难忘体验
3. 改善流向布法罗河的水源水质
1. Restore and stabilize riparian corridors.
2. Provide moments of intensified native plantings for distinctive and memorable experiences.
3. Improve water quality flowing to Buffalo Bayou.
Image by: Design Workshop, Inc.


扩建的步道系统为游人提供了多重选择，使其得以探索并了解植物园的生态环境。一段极具教育意义的环形步道让即使是最年轻的学习者都能融入到当地的所有生态系统中
The expanded trail network gives visitors multiple options to explore and learn about the ecologies of the Arboretum. A short educational loop allows even the youngest learners to engage in all the ecologies on-site.
Image by: Design Workshop, Inc.


每个步道类型的特色都展示出各生态系统所特有的典型原生植栽，并与其贯穿的栖息地相互呼应
The character of each trail typology responds to the habitat it traverses while displaying representative native plantings endemic of each ecology.
Image by: Design Workshop, Inc.


挑高的木板桥使游人得以眺望休斯顿最优美的景观瑰宝之一——极富历史意义的布法罗河口
The trail experience crescendos with an elevated boardwalk giving visitors a look out over one of Houston’s most cherished assets - the historic Buffalo Bayou.
Image by: Design Workshop, Inc.


Project Statement

A critical anchor within beloved Memorial Park, the 155-acre Houston Arboretum and Nature Center is devastated by weather extremes from drought to hurricanes. Fundamental to the plan that guides the Arboretum’s renewal is an exhaustive assessment of the site’s natural and cultural heritage, diagnosis of the impacts of climate change, and extensive stakeholder engagement. The plan outlines a more resilient evolution for the Arboretum and is a model for other regions facing similar threats.

Project Narrative

The Challenge
Located along Buffalo Bayou, the Houston Arboretum & Nature Center is a 155-acre regional resource that serves as a critical refuge for native plants and animals and a hub for environmental education in the city. The Arboretum is a discrete part of the 1,500-acre Memorial Park designed in 1925 by the landscape architecture and planning firm of Hare & Hare. Developed in the 1950s, the site had evolved to present plants and systems related to more idealize ecological habitats. However, recent hurricanes and drought have taken their toll on its landscape as evidenced by 48-percent tree canopy mortality and the significant presence of invasive species. The primary challenge of the Master Plan is to integrate the site’s ecological and cultural history with modern demands into a responsive, flexible plan of renewal.

“The mission of the Arboretum and Nature Center is to provide education about the natural environment to people of all ages and to protect and enhance the Arboretum as a haven and as a sanctuary for native plants and animals.”

Active Listening
Key to crafting a Master Plan that is specific and relevant is starting with an understanding of values and vision. The stakeholder engagement process was extensive, utilizing multiple meetings with a diverse range of public and private sector groups and individuals including teachers, users, Arboretum staff and board members, City of Houston staff, Memorial Park Conservancy board members, donors and others. The process successfully provided an interactive forum for dialogue amongst stakeholders and valuable learning experiences for all participants. At the workshops, stakeholders identified two primary goals – achieving landscape diversity and balancing programmed and “wild” spaces. With a populace so deeply affected by the canopy loss, the landscape architects had to carefully navigate between a desire to restore the previous character of the place and a results-oriented plan founded on the reality of ecological systems in flux. The design team rallied the community around a new trajectory for this landscape—one of a resilient system of varied ecologies changing over time.

The preferred “Corridors” alternative addresses stakeholders’ goals for restoring the natural habitats of the Arboretum in a manner that is authentic to its cultural and ecological context while incorporating interpretive programming activities across the site. The resultant plan lays the foundation for a world-class landscape capable of inspiring visitors and citizen activists who are committed to engagement with the Arboretum and spreading its significance and interpreted messages throughout the region.

Ecological Forensics
Using a forensic approach, the team of landscape architects analyzed the specific site conditions that led to drastic, but not total, canopy mortality. Extensive site analyses of soil-types, drainage patterns, tree canopy, plant diversity and other factors were conducted to understand baseline conditions. The interdisciplinary team of scientific experts and designers conducted research using GIS and field analysis. This analysis revealed that the areas with highest tree mortality rates (those with 70 percent tree mortality or greater) occurred in areas more characteristic of prairie landscapes such as silty clay loam soils and “pimple-dimple” geologic formations where micro-ecologies exist. Canopy trees growing in the “dimple” areas, where water collects, developed shallow endless extensive root systems and experienced the greatest canopy loss during the drought. Paradoxically, canopy trees growing on the raised “pimples” developed deeper and more extensive root systems and survived the drought.

This ecological pattern—revealed only by the recent change in climate—suggested a new landscape mosaic of more varied ecologies. A process of environmental overlays helped determine where optimum conditions existed on-site for varied landscape typologies. For example, prairie currently comprises only 2-percent of the existing site, but 49-percent of the site has characteristics conducive to prairie. This research helped decision makers embrace the radical changes proposed in the plan (23 percent of the site or 12 times the amount of prairie as currently exists) projected to result in a landscape more resilient to future stresses. The new composition of landscape character zones also results in a 420 percent increase in on-site ecotones, a landscape type rich in biodiversity. Prairie, savannah, bog, hardwood forests, and riparian woods are to be developed not as a static spatial condition, but as a potentially shifting and responsive group of interrelated systems. Each is set in motion through specific removals and new plantings arrayed according to particular soil and hydrologic conditions.

Programmatic Balance
The Master Plan improves the infrastructure related to how people use the site in order to diversify their experience, leading to better enjoyment and understanding of the site’s ecology. The Arboretum currently hosts 180,000 visitors a year and is a valued educational and open space asset for the Houston region. School groups visit the site regularly for nature-based education, and there are frequent on-site adult classes. The Master Plan explored expanding the program services offered on-site, but was also very conscious of its carrying capacity to achieve a balance of unprescribed natural areas and programmed areas. Benchmarks with metrics of nature versus programmed space were drawn from relevant botanical gardens and arboreta. Decision makers endorsed the Master Plan’s recommendations that result in similar characteristics as these precedents.

More than 85-percent of the site will be preserved as natural area, and the focus of programmed area will be organized along a diverse network of trails. Currently, there are six trail types based on existing landscape character zones totaling 20,150 linear feet. The plan incorporates 11 educational trails based on new or enhanced landscape character zones and experiences. The linear footage of all trails increased to 39,061 feet (an increase of 94-percent). These changes allow more opportunity for visitors to experience a wider cross-section of the Houston eco-region while visiting the Arboretum.

With expanded infrastructure, however, comes the potential to increase the impervious coverage levels of the site and negatively impact hydrology and water quality, especially as a watershed flowing into Buffalo Bayou. To mitigate the potential effects of increased infrastructure on local ecologies, the Master Plan proposes the demolition of existing asphalt parking areas and the replacement of these permanent parking areas with more permeable surfaces. The plan also proposes stabilized native turf grasses for overflow parking areas and integral rainwater collection to mitigate the effects of impervious cover. The plan integrates new buildings, trails and other built features fitted to the topography in order to minimize erosion that may negatively affect water quality. Wet ponds increase the habitat diversity of the Arboretum through vegetation that filters and cleans water on-site.

Progressive Resilience
As a response to ecological crisis, the Master Plan focuses on developing ecosystem resilience and holds the potential to be a model for southeast Texas and other areas undergoing prolonged drought. As important as the original design of these systems is, the management regime planned to regularly assess ecological performance and brace for potential uncertainty. Utilizing a complex management matrix and an dedicated group of volunteers, the Master Plan defines strategic interventions to initiate new dynamic ecologies. The detritus of tree loss will be chipped and repurposed to help liner stock plantings retain moisture and provide vital organic matter back to a soil degraded by drought. Thickets of invasive species will be removed, fortifying canopy strongholds and other natives. Volunteers will plant drifts of liner stock in waves. Swaths of prairie and savannah will be seeded and regenerated by annual mowing or controlled burnings. The strategy manages toward a resilient set of dynamic and evolving systems, fulfilling the Arboretum’s mission to interpret the land as a collection of natural habitats and interrelated systems rather than as a collection of trees.


项目信息

设计与施工团队
Design Workshop——主要顾问（美国德克萨斯州奥斯汀市）团队成员：
库尔特·卡伯特森，美国景观设计师协会理事
丽贝卡·伦纳德
史蒂芬·斯皮尔斯，美国景观设计师协会会员
康纳斯·拉德纳
艾米莉·赖辛尔
玛丽·马西尼奇，美国景观设计师协会助理会员
劳拉·布莱恩特
亚伦·奥德兰德
克莱尔·亨佩尔
杰森·福斯特，美国景观设计师协会会员
劳伦·法斯克
乔纳森·博尔金，总监，美国建筑师协会会员
顾问团队
Reed|Hilderbrand——景观设计顾问团队（美国马萨诸塞州，沃特敦）：
道格·里德，美国景观设计师协会理事
约瑟夫·詹姆斯，美国景观设计师协会会员
加勒特·牛顿，美国景观设计师协会会员
吉尹·尹，美国景观设计师协会学生会员
沃尔特·P·穆尔——土木工程师
生态设计团队：
ETM Associates, LLC
W. Todd Watson, PhD, BCMA
SWCA Environmental Consultants
Lake|Flato – Architecture

Project Resources

Design & Construction Team
Design Workshop - Prime Consultant (Austin, TX) Team Members:
Kurt Culbertson, FASLA
Rebecca Leonard
Steven Spears, ASLA
Conners Ladner
Emily Risinger
Mary Martinich, Associate ASLA
Laura Bryant
Aaron Odland
Claire Hempel
Jason Ferster, ASLA
Lauren Fasic
Jonathan Boelkins, Studio Director, AIA
Consultant Team
Reed|Hilderbrand – Landscape Architecture (Watertown, MA)
Doug Reed, FASLA
Joseph James, ASLA
Garrett Newton, ASLA
Jihyoon Yoon, Student ASLA
Walter P. Moore - Civil Engineering
Ecosystem Design Group
ETM Associates, LLC
W. Todd Watson, PhD, BCMA
SWCA Environmental Consultants
Lake|Flato – Architecture