融合景觀連通性的城鎮(zhèn)規(guī)劃與生物多樣性生態(tài)服務(wù)效能優(yōu)化

著：(澳)陳思清 汪潔瓊

譯：王南

Authors: (Australia) CHEN Si-qing, WANG Jie-qiong

Traslator: WANG Nan

融合景觀連通性的城鎮(zhèn)規(guī)劃與生物多樣性生態(tài)服務(wù)效能優(yōu)化

著：(澳)陳思清 汪潔瓊

譯：王南

Authors: (Australia) CHEN Si-qing, WANG Jie-qiong

Traslator: WANG Nan

隨著世界范圍內(nèi)瀕危物種滅絕速率的日益增長(zhǎng)，生物多樣性已成為生態(tài)系統(tǒng)服務(wù)中最重要的組成部分之一。無(wú)論地區(qū)、區(qū)域還是全球尺度范疇，生物多樣性的保護(hù)都是保持生態(tài)系統(tǒng)活力的關(guān)鍵。景觀連通性包含兩層含義，既是對(duì)景觀自然結(jié)構(gòu)的描述，也包含特定物種對(duì)該結(jié)構(gòu)的響應(yīng)，它為景觀連通性原理應(yīng)用于景觀規(guī)劃實(shí)踐提供了理論基礎(chǔ)，尤其是對(duì)那些通過(guò)生態(tài)系統(tǒng)服務(wù)的整合來(lái)改善環(huán)境影響的項(xiàng)目，這種理論基礎(chǔ)的作用更為突出?；诿绹?guó)東南部生態(tài)城鎮(zhèn)開(kāi)發(fā)項(xiàng)目的案例分析，本文試圖探索出能夠促進(jìn)景觀連通性并推進(jìn)生物多樣性保護(hù)的設(shè)計(jì)思路?；诘乩硇畔⑾到y(tǒng)(GIS)與空間數(shù)據(jù)分析(FRAGSTATS)，本研究旨在量化美國(guó)東南部以林地和林帶為特色的景觀連通性。在美國(guó)東南部，由于房地產(chǎn)業(yè)持續(xù)擴(kuò)張、新增住宅不斷開(kāi)發(fā)，大量擁有自然景觀的區(qū)域正經(jīng)歷著城鎮(zhèn)化進(jìn)程。研究結(jié)果表明，通過(guò)增加棲息地斑塊面積以及它們之間的連通性，在基地內(nèi)已建綠色基礎(chǔ)設(shè)施中增植新的林帶可顯著增加景觀連通性，從而有效地提供生態(tài)系統(tǒng)服務(wù)。結(jié)論部分，本研究聚焦在如何通過(guò)更高的景觀連通性來(lái)實(shí)現(xiàn)新城發(fā)展需求與生態(tài)系統(tǒng)服務(wù)供給兩者間的平衡，也因此提出了設(shè)計(jì)干預(yù)需將宜居性與可持續(xù)性并重的觀點(diǎn)。

風(fēng)景園林；景觀連通性；生態(tài)系統(tǒng)服務(wù)；生物多樣性保護(hù)；景觀規(guī)劃

1 引言

“景觀連通性”這一概念強(qiáng)調(diào)的是物種特性與景觀結(jié)構(gòu)在決定棲息地斑塊內(nèi)部有機(jī)體運(yùn)動(dòng)時(shí)的互動(dòng)[1]。人類活動(dòng)，如農(nóng)業(yè)發(fā)展、商業(yè)造林、基礎(chǔ)設(shè)施建設(shè)和城鎮(zhèn)化等，已導(dǎo)致棲息地破碎化，即原棲息地的喪失、棲息地斑塊面積減少或隔離，以及景觀連通性的降低[2]。然而，這些關(guān)鍵性的因素并未受到科學(xué)研究的重視，許多實(shí)際運(yùn)行的土地開(kāi)發(fā)項(xiàng)目則是號(hào)稱已為景觀連通性的提高做出了努力。實(shí)際上，由于缺乏對(duì)景觀連通性含義的正確理解，這些研究和項(xiàng)目反而可能會(huì)減小景觀連通性對(duì)土地管理和生物多樣性保護(hù)的潛在效用。根據(jù) Taylor等人(1993)最初的定義，景觀連通性是“景觀推動(dòng)或阻礙資源斑塊間運(yùn)動(dòng)的程度”[3]，這一定義強(qiáng)調(diào)了景觀內(nèi)部棲息地或土地利用的種類、數(shù)量及布局對(duì)種群動(dòng)態(tài)及群落結(jié)構(gòu)產(chǎn)生變化的影響。景觀連通性應(yīng)將上述兩層含義結(jié)合，既包含對(duì)景觀自然結(jié)構(gòu)的描述(結(jié)構(gòu)連通性)，也包含特定物種對(duì)該結(jié)構(gòu)的響應(yīng)(功能連通性)，這正是景觀連通性原理應(yīng)用于景觀規(guī)劃及設(shè)計(jì)實(shí)踐的理論基礎(chǔ)。基于地理信息系統(tǒng)(GIS)，本研究對(duì)景觀連通性進(jìn)行了量化。通過(guò)對(duì)美國(guó)南部某住宅開(kāi)發(fā)項(xiàng)目的案例研究，本文進(jìn)一步探索了景觀連通性的含義及其在城市規(guī)劃中的應(yīng)用。

生態(tài)系統(tǒng)服務(wù)已被定義為人們從不同生態(tài)系統(tǒng)中能直接或間接獲取的利益，如大自然提供的生物多樣性為人類提供的各種益處，包括食物、纖維、氣候及溫度的調(diào)節(jié)、授粉以及能夠加強(qiáng)不同人群福祉的審美價(jià)值觀[4]。然而，人口增長(zhǎng)、城鎮(zhèn)化及相關(guān)的自然資源開(kāi)發(fā)已導(dǎo)致全世界約60%的生態(tài)系統(tǒng)服務(wù)普遍退化[4]。要逆轉(zhuǎn)這一趨勢(shì)就意味著必須盡快改變?nèi)藗儾豢沙掷m(xù)的現(xiàn)代生活方式以及對(duì)生態(tài)系統(tǒng)服務(wù)認(rèn)知的缺乏。因此，如何使人們正確理解生態(tài)系統(tǒng)提供服務(wù)的方式就變得至關(guān)重要，人們對(duì)于生態(tài)系統(tǒng)服務(wù)和產(chǎn)品價(jià)值的認(rèn)知亟需提升。景觀和城市規(guī)劃的從業(yè)者也必須意識(shí)到人類，無(wú)論城市居民或鄉(xiāng)村居民，都只是地球上棲息的物種之一，他們必須摒棄將生態(tài)系統(tǒng)服務(wù)視為理所應(yīng)當(dāng)?shù)膽B(tài)度，參與到保護(hù)生態(tài)系統(tǒng)的活動(dòng)中來(lái)，才能更好地保持生態(tài)系統(tǒng)服務(wù)的可持續(xù)供給。

生物多樣性具有多種定義及多重考量標(biāo)準(zhǔn)。它可以被定義為“地球上生命的多樣性”[4]，也常被認(rèn)為是“支撐生態(tài)系統(tǒng)過(guò)程的調(diào)節(jié)者，最終實(shí)現(xiàn)生態(tài)系統(tǒng)服務(wù)或提供產(chǎn)品”[5]。可以說(shuō)，生物多樣性是最重要的生態(tài)系統(tǒng)服務(wù)，而生物多樣性的保護(hù)能夠在不同的空間尺度上實(shí)現(xiàn)。在全球或區(qū)域范圍內(nèi)，2011年通過(guò)的《生物多樣性公約》確立了愛(ài)知生物多樣性目標(biāo)，即為保護(hù)和促進(jìn)全球生物多樣性而制定的一系列目標(biāo)。其中，目標(biāo)11呼吁要加強(qiáng)17%的陸地面積(不包括南極)的保存及保護(hù)，尤其是生物多樣性受到威脅的區(qū)域更應(yīng)努力達(dá)到這一目標(biāo)。該面積相當(dāng)于2 294萬(wàn)km2，約等于加拿大、中國(guó)和印度3個(gè)國(guó)家的面積總和[6]。從大的空間尺度及長(zhǎng)期視角談保護(hù)生物多樣性固然有其重要意義，但保存及保護(hù)措施的具體落實(shí)卻只能在地區(qū)或場(chǎng)地范圍內(nèi)實(shí)現(xiàn)。就場(chǎng)地層面來(lái)看，生物多樣性會(huì)受到土地利用方式(如農(nóng)業(yè)發(fā)展)的巨大影響[7]。它與4個(gè)影響棲息地質(zhì)量的因素相關(guān)：每個(gè)威脅的相對(duì)影響、每個(gè)棲息地對(duì)每個(gè)威脅的相對(duì)敏感度、威脅源與棲息地間的距離、以及該土地利用方式受到法律保護(hù)的程度。此外，威脅有時(shí)正是人類主導(dǎo)的景觀本身，如農(nóng)田或城市地區(qū)[8]。本研究將從棲息地連通性和生物多樣性保護(hù)入手，對(duì)場(chǎng)地層面的設(shè)計(jì)干預(yù)進(jìn)行調(diào)查研究。

1 黑色地帶的位置及區(qū)域環(huán)境，阿拉巴馬州黑色地帶的傳統(tǒng)縣及哈德遜農(nóng)場(chǎng)的位置Location and regional context of the black belt, traditional counties in the Alabama black belt, and location of Hudson farm

2 案例研究的項(xiàng)目場(chǎng)地

2.1 林帶

美國(guó)南部廣袤的鄉(xiāng)村景觀以林帶喬木或樹(shù)叢作為顯著特征。除了限定空間與定義邊界，林帶在鄉(xiāng)村景觀中也提供了許多其他的生態(tài)系統(tǒng)服務(wù)，例如為人類提供食物、衣物、庇護(hù)，提升視覺(jué)質(zhì)量，維持鄉(xiāng)村景觀的真實(shí)性等。這些林帶的生態(tài)系統(tǒng)服務(wù)可就其彼此間的關(guān)系進(jìn)行評(píng)估[9-13]。然而，林帶在生物保護(hù)中最重要的功能在于它們?yōu)橹T如鳥(niǎo)、鼠、蝴蝶等野生動(dòng)物提供了重要的棲息地。與此同時(shí)，具備生態(tài)廊道功能的林帶可以保持并增大景觀連通性，保持生態(tài)可變性，從而保護(hù)并提升景觀的生物多樣性[14-18]。

由高聳的林帶圍合起來(lái)的土地所形成的斑塊景觀是美國(guó)鄉(xiāng)村為人熟知的傳統(tǒng)特征。林帶實(shí)際上是帶狀的樹(shù)木、樹(shù)叢或林地，它們通常是野生動(dòng)物的重要棲息地，對(duì)景觀的視覺(jué)質(zhì)量也具有十分重要的作用。本研究試圖通過(guò)對(duì)哈德遜農(nóng)場(chǎng)項(xiàng)目進(jìn)行案例分析，闡明景觀連通性如何得以量化。哈德遜農(nóng)場(chǎng)位于美國(guó)東南地區(qū)的“黑色地帶”?！昂谏貛А弊畛跏侵赴⒗婉R州中部及密西西比州東北部的大草原和黑色土壤，但現(xiàn)已被長(zhǎng)期用來(lái)指稱美國(guó)南部的一個(gè)非裔美國(guó)人口眾多的廣闊區(qū)域。通常認(rèn)為，“黑色地帶”覆蓋了佐治亞州中部、佛羅里達(dá)州北部、密西西比州西部、阿拉巴馬州中部及南部、路易安娜州中部及東部、卡羅萊納州東部及北部、弗吉尼亞州東南部的廣大區(qū)域。哈德遜農(nóng)場(chǎng)正位于這一“黑色地帶”之上，是阿拉巴馬州首府蒙哥馬利縣東南部的一個(gè)郊區(qū)(圖1)。哈德遜農(nóng)場(chǎng)的最顯著的特色正是這種林帶喬木或樹(shù)叢所形成的景觀。林帶構(gòu)建了一系列斑塊所形成的網(wǎng)絡(luò)，創(chuàng)造出高聳的喬木林帶和灌木形成的廊道環(huán)繞著較低的田野的景觀。

林帶和林地，對(duì)于鳥(niǎo)類、蜜蜂、鼠類、蝴蝶等野生動(dòng)物而言，是重要棲息地(圖2)。同時(shí)，具備生態(tài)斑塊功能的林地和具備生態(tài)廊道功能的林帶可在保持棲息地類型的多樣性和景觀連通性方面相輔相成。在這一案例中，林帶和林地形成的斑塊—廊道—基質(zhì)對(duì)于保護(hù)及促進(jìn)場(chǎng)地的生物多樣性至關(guān)重要。林帶廊道和林地斑塊作為項(xiàng)目場(chǎng)地內(nèi)的綠色基礎(chǔ)設(shè)施，不僅使鄉(xiāng)村景觀具備了強(qiáng)烈的場(chǎng)所感，而且能喚起人們對(duì)美國(guó)鄉(xiāng)村的情感共鳴[19-20]。因此，必須對(duì)林帶廊道和林地斑塊進(jìn)行深入探究，通過(guò)生態(tài)景觀規(guī)劃和創(chuàng)新性城市設(shè)計(jì)策略將其融入土地開(kāi)發(fā)項(xiàng)目。

2 哈德遜農(nóng)場(chǎng)上的灌木樹(shù)籬、草地、林地棲息地及生物多樣性Hedgerow, grassland, and woodland habitat and biodiversity on Hudson Farm

3 場(chǎng)地的高程、坡度、朝向分析Elevation, slope and slope aspect analysis of the site

2.2 地形特征

項(xiàng)目基地的顯著特征是一條山脊線將整個(gè)場(chǎng)地分成了若干個(gè)次一級(jí)匯水區(qū)(圖3)?；氐淖罡唿c(diǎn)310英尺(譯者注：約94m)坐落于場(chǎng)地的南側(cè)，而基地的最低點(diǎn)227英尺(譯者注：約69m)則坐落于場(chǎng)地的北側(cè)。哈德遜農(nóng)場(chǎng)以地形稍有起伏的草原和疏林草地景觀為特征。

GIS的坡度分析顯示整個(gè)基地較為平坦，大部分的土地的坡度都在7%以下(圖3)。坡度朝向分析則顯示：山脊線南側(cè)的大部分地塊都是西向或西南向的，而基地北側(cè)的大部分地塊朝向都是北向或者東北向的(圖3)。基于坡度朝向的分析，可以進(jìn)一步地考慮日照、利用太陽(yáng)能作為可替換能源方式的使用潛能等。

3 景觀連通性

3.1 結(jié)構(gòu)連通性

通常情況下，使用“連通性”這一術(shù)語(yǔ)來(lái)強(qiáng)調(diào)結(jié)構(gòu)層面，景觀連通性就簡(jiǎn)單地等同于景觀促進(jìn)傳播的線性特征，如自然連接的線性廊道。這種意義上的連通性意味著，從A出發(fā)沿一定路線可到達(dá)B。而在網(wǎng)絡(luò)系統(tǒng)中(圖4)，如果A到B有更多可選路線，就認(rèn)為該網(wǎng)絡(luò)系統(tǒng)聯(lián)系更緊密，即連通性更高。

4 點(diǎn)A至點(diǎn)B的路線數(shù)量，體現(xiàn)環(huán)密度及自然連通性Number of travelling routes from point A to point B, showing loop density and physical connectivity

5 林帶廊道及連通性(a)飛地；(b)飛地間距離；(c)飛地缺失；(d)網(wǎng)絡(luò)連通性；(e)環(huán)及可選路線；(f)交叉影響Hedgerow corridor and connectivity: (a) stepping stone; (b) distance between stepping stone; (c) loss of stepping stone; (d) network connectivity; (e) loops and alternatives; (f) intersection effect

6 哈德遜農(nóng)場(chǎng)上作為景觀基礎(chǔ)設(shè)施的林帶廊道(a)航拍林帶廊道與場(chǎng)地邊界的疊加；(b)場(chǎng)地內(nèi)作為生態(tài)基礎(chǔ)設(shè)施的林帶廊道及林地斑塊Hedgerow corridors as landscape infrastructure on Hudson Farm (a) aerial photo overlaid with site boundary, and (b) hedgerow corridors and woodland patches as ecological infrastructure on site

3.2 功能連通性

自然連通性通常以網(wǎng)狀系統(tǒng)中環(huán)的數(shù)量來(lái)衡量。但在景觀生態(tài)學(xué)中，通常采用的連通性衡量方法不僅注重自然連接的線性廊道，也關(guān)注斑塊區(qū)域以及斑塊間距離對(duì)斑塊間運(yùn)動(dòng)的影響，即非自然連接的廊道，如某些物種用作連接廊道的飛地(圖5)。這種連接被稱作功能連通性[21]。

寬度和連通性是廊道五大主要功能—棲息地、通道、過(guò)濾、源、匯—的主要控制因素[9,22-23]。廊道內(nèi)缺口對(duì)某一物種運(yùn)動(dòng)的影響取決于該缺口相對(duì)物種運(yùn)動(dòng)幅度的長(zhǎng)度以及廊道和缺口間的差別。然而，一排飛地(小斑塊)在廊道和非廊道之間只具備中等連通性，因此它只能為斑塊間的內(nèi)部物種運(yùn)動(dòng)起到中等作用(圖5a)。對(duì)于高度視覺(jué)導(dǎo)向的物種來(lái)說(shuō)，其在飛地之間運(yùn)動(dòng)的有效距離則取決于其看到每個(gè)連續(xù)飛地的視覺(jué)能力(圖5b)。一個(gè)用作其他斑塊間運(yùn)動(dòng)飛地的小斑塊的缺失，通常會(huì)抑制運(yùn)動(dòng)進(jìn)而加大斑塊隔離(圖5c)。而對(duì)大斑塊間的飛地群進(jìn)行最優(yōu)空間布局可以生成備選或冗余路線，同時(shí)在大斑塊間保持整體的線性導(dǎo)向陣列[30]。許多研究均已證明，這種結(jié)構(gòu)可以促進(jìn)野生動(dòng)物的運(yùn)動(dòng)[21-22, 24-32]。

3.3 棲息地連通性

哈德遜農(nóng)場(chǎng)是一個(gè)家庭農(nóng)場(chǎng)，它位于阿拉巴馬州蒙哥馬利縣郊區(qū)，占地2 200英畝(譯者注：約合8.9km2)。該農(nóng)場(chǎng)土地曾主要用于牛群放牧和干草收割。場(chǎng)地內(nèi)的景觀要素，如樹(shù)、洞穴、林帶、谷倉(cāng)和籬笆，構(gòu)成了蒙哥馬利縣城鄉(xiāng)結(jié)合部的獨(dú)特地標(biāo)。深入了解和理解場(chǎng)地是做好規(guī)劃設(shè)計(jì)的基本要求，而對(duì)諸如樹(shù)、洞穴、林帶、谷倉(cāng)和籬笆這些與眾不同的地標(biāo)進(jìn)行保護(hù)和加強(qiáng)，則能保持該場(chǎng)地獨(dú)一無(wú)二的特點(diǎn)。地產(chǎn)開(kāi)發(fā)的目標(biāo)是打造一個(gè)步行為主、混合使用的緊湊型新社區(qū)，并不采取用途單一的傳統(tǒng)郊區(qū)發(fā)展模式。在可持續(xù)發(fā)展的道路上，應(yīng)注重打造完整的社區(qū)和小鎮(zhèn)，而非零星式的郊區(qū)發(fā)展[33]。

在哈德遜農(nóng)場(chǎng)，景觀中的林帶以廊道的形式存在(圖6)，是支撐生物多樣性的重要棲息地。農(nóng)場(chǎng)區(qū)域的航拍照片展現(xiàn)了該場(chǎng)地的景觀結(jié)構(gòu)(圖6a)。農(nóng)場(chǎng)周圍是大面積的河流廊道和濕地，為候鳥(niǎo)和其他野生動(dòng)物提供了重要的棲息地。哈德遜農(nóng)場(chǎng)之所以獨(dú)特，就在于它擁有大面積的森林斑塊、開(kāi)闊的田野、林帶廊道以及高林帶圍起的大片“景觀空間”等景觀要素。高大的林帶喬木和樹(shù)叢，或點(diǎn)綴、或包圍著開(kāi)闊的田野，放眼望去，農(nóng)場(chǎng)上的林帶和喬木呈現(xiàn)出深遠(yuǎn)的視覺(jué)感受，增強(qiáng)了農(nóng)場(chǎng)的場(chǎng)所感(圖6b)。

4 景觀尺度的連通性量化

4.1 基于GIS的景觀指標(biāo)

景觀連通性的量化有多種方法。例如，基于福爾曼(Forman)的城市生態(tài)角度[9]，利用聯(lián)結(jié)與節(jié)點(diǎn)的數(shù)量，可通過(guò)一個(gè)簡(jiǎn)易公式對(duì)連通性(con)進(jìn)行計(jì)算。

con= L / 3 (V-2) (1)

其中，

L = 聯(lián)結(jié)的數(shù)量；

V = 節(jié)點(diǎn)的數(shù)量。

這種方法在景觀聯(lián)結(jié)與節(jié)點(diǎn)均容易識(shí)別的精密尺度下可能方便使用，但在景觀尺度上，場(chǎng)地情況高度多樣化、復(fù)雜化(比如有不同形式的連通性)，就需要使用基于GIS的新方法對(duì)連通性進(jìn)行量化。

很多基于GIS的景觀指標(biāo)都是由景觀生態(tài)學(xué)家和科學(xué)家們提出并供公眾使用的[34]。FRAGSTATS是美國(guó)麻省大學(xué)景觀生態(tài)實(shí)驗(yàn)室開(kāi)發(fā)的程序，用來(lái)計(jì)算不同地圖模式下多種景觀指標(biāo)(包括景觀連通性)，其初始軟件(版本2)于1995年向公眾發(fā)布，與之聯(lián)合發(fā)布的是美國(guó)農(nóng)業(yè)部的《森林服務(wù)通用技術(shù)報(bào)告》[5]。本文運(yùn)用了其版本3.3，該版本可從該實(shí)驗(yàn)室網(wǎng)站下載。FRAGSTATS對(duì)連通性的計(jì)算均基于連通性指標(biāo)(表1)。

例如，連通性指標(biāo)(con)可以計(jì)算為：

其中，

Cijk=基于用戶指定的距離閾值，屬同一斑塊類型的斑塊j與斑塊k間的接合點(diǎn)(0=未接合，1=接合)。

ni=每一斑塊類型i的景觀內(nèi)部的斑塊數(shù)量。

在這個(gè)方程式中，連通性等于所有同類型斑塊間功能性接合點(diǎn)的數(shù)量(Cijk總和，如斑塊j和k不在彼此的指定距離內(nèi)，那么Cijk=0；如斑塊j和k在指定距離內(nèi)，那么Cijk=1)，除以所有同類型斑塊間的所有可能存在的接合點(diǎn)總數(shù)，再乘以100以轉(zhuǎn)化為百分比。因此連通性數(shù)值在0～100之間。當(dāng)景觀僅由一個(gè)斑塊構(gòu)成，或所有類別只有一個(gè)斑塊，或景觀內(nèi)部所有斑塊均不互相連接(即在用戶指定的另一個(gè)同類斑塊的距離閾值內(nèi))時(shí)，連通性=0。當(dāng)景觀內(nèi)部每個(gè)斑塊均有連接時(shí)，連通性=100[34]。

4.2 數(shù)據(jù)輸入與模型參數(shù)化

使用FRAGSTATS空間格局分析程序，需要準(zhǔn)備好可識(shí)別格式的文件作為GIS數(shù)據(jù)輸入程序中，以計(jì)算景觀指標(biāo)。在運(yùn)行并輸出統(tǒng)計(jì)數(shù)據(jù)前，該程序必須進(jìn)行正確的參數(shù)化(圖7)。關(guān)于FRAGSTATS程序、輸入數(shù)據(jù)準(zhǔn)備、模型參數(shù)化及輸出數(shù)據(jù)格式的細(xì)節(jié)請(qǐng)見(jiàn)該軟件網(wǎng)站。

表1 FRAGSTATS中使用的連通性指標(biāo)Tab.1 Connectivity metrics used in FRAGSTATS

7 FRAGSTATS程序參數(shù)化界面Parameterization interface of the FRAGSTATS program

4.3 實(shí)證研究：哈德遜農(nóng)場(chǎng)

為保障景觀內(nèi)部野生動(dòng)物活動(dòng)并增強(qiáng)生物多樣性，維持廊道網(wǎng)絡(luò)是設(shè)計(jì)功能完整且健康的景觀時(shí)需要遵循的基本原則。在哈德遜項(xiàng)目的總體規(guī)劃制定過(guò)程中，林帶之間相互連接，且有連貫的喬木覆蓋。這一理念為諸多景觀生態(tài)學(xué)家所倡導(dǎo)[35]。該網(wǎng)絡(luò)疊加于排水系統(tǒng)和已有林帶之上。其空間布局也考慮了如農(nóng)場(chǎng)主與工人關(guān)系等歷史因素[36]?；谝陨嫌^點(diǎn)，對(duì)已有林帶的研究就此展開(kāi)(圖8)。

為了進(jìn)一步增加連通性，提出新的林帶與已有林帶連接以形成一個(gè)林帶網(wǎng)絡(luò)。該網(wǎng)絡(luò)將作為綠色基礎(chǔ)設(shè)施網(wǎng)絡(luò)或生態(tài)基礎(chǔ)設(shè)施網(wǎng)絡(luò)，兼具設(shè)計(jì)與生態(tài)功能?；灸康氖菫榱苏故舅鼈?yōu)槭裁匆B接起來(lái)，并如何連接起來(lái)。左側(cè)圖(圖8a)顯示了已有林帶，中間圖(圖8b)的紅色區(qū)域表示新增種植的林帶，右側(cè)圖(圖8c)則是已有林帶與新增種植林帶的疊加效果。

8 哈德遜農(nóng)場(chǎng)上已有林帶與計(jì)劃種植林帶的連接Existing and proposed hedgerow connection on Hudson Farm

9 用于包含生物多樣性及相關(guān)生態(tài)系統(tǒng)服務(wù)的景觀規(guī)劃的尺度思考框架Scale thinking framework for landscape planning considering biodiversity and related ecosystem services

5 結(jié)果

根據(jù)FRASTATS的空間格局分析程序提供的數(shù)據(jù)結(jié)果可以發(fā)現(xiàn)，通過(guò)整合已建綠色基礎(chǔ)設(shè)施和新增的林帶廊道，該地的景觀連通性已提升40%(表2)。新增的林帶種植在現(xiàn)有的農(nóng)田邊、廢棄的農(nóng)場(chǎng)設(shè)備原址且遍布牧場(chǎng)，它們連接起現(xiàn)有的殘存樹(shù)木及樹(shù)叢，形成了互相聯(lián)結(jié)的林帶網(wǎng)絡(luò)。因此，在未犧牲現(xiàn)有作為核心棲息地的大型景觀斑塊的情況下，就可以實(shí)現(xiàn)40%的連通性增長(zhǎng)。新計(jì)劃的林帶重新連接起破碎的廊道，大幅增加了整體景觀連通性。這表明保持景觀完整性以及自然植被廊道至關(guān)重要。

分析表明，可將FRAGSTATS同GIS結(jié)合使用，能計(jì)算出景觀尺度的連通性及其他參數(shù)。但表2中的數(shù)據(jù)結(jié)果必須謹(jǐn)慎解讀。比如，連通性通過(guò)“連接性”和“內(nèi)聚力”來(lái)衡量(表1、2)；以公式(2)測(cè)量的“連接性”提高了40.7%，而景觀“內(nèi)聚力”卻未以同等幅度增加，反而略有下降[34]。該例表明，設(shè)計(jì)干預(yù)可以改變場(chǎng)地生態(tài)，因此必須在設(shè)計(jì)實(shí)施后對(duì)結(jié)果進(jìn)行恰當(dāng)評(píng)估以實(shí)現(xiàn)設(shè)計(jì)干預(yù)，而數(shù)字技術(shù)的進(jìn)步已使這一過(guò)程變得越發(fā)容易。

6 討論

對(duì)生物多樣性及相關(guān)生態(tài)系統(tǒng)服務(wù)的保護(hù)已成為全球性的挑戰(zhàn)，需以跨越時(shí)間尺度與空間尺度的系統(tǒng)方法來(lái)應(yīng)對(duì)。生物多樣性規(guī)劃需要設(shè)計(jì)能力能強(qiáng)調(diào)對(duì)這種復(fù)雜性的考慮。跨尺度的系統(tǒng)思考方法[36]可在全球及區(qū)域尺度下對(duì)棲息地連通性及生物多樣性保護(hù)進(jìn)行深入解讀。生態(tài)系統(tǒng)科學(xué)研究已顯示出多尺度分析的必要性，并將特定尺度下輸入的分辨率，以及評(píng)估過(guò)程考慮在內(nèi)。在景觀規(guī)劃中，跨尺度的思考能夠檢驗(yàn)土地系統(tǒng)在場(chǎng)地、地區(qū)、區(qū)域、國(guó)家甚至全球尺度下相互之間的聯(lián)系和影響(圖9)?？绯叨鹊乃伎紝?duì)于從整體上把握?qǐng)龅丶捌浯蟊尘坝葹橹匾部梢詭椭斫獠煌叨认碌耐阶饔昧?，并將這些跨尺度的功能聯(lián)系在一起，從而更好的、更整體性的把握相互聯(lián)系的景觀過(guò)程，從而為設(shè)計(jì)策略尋找思路。

表2 哈德遜農(nóng)場(chǎng)新計(jì)劃林帶種植前后的景觀連通性指數(shù)對(duì)比Tab.2 Comparison of landscape connectivity index before and after proposed hedgerow on Hudson Farm

生物多樣性及相關(guān)生態(tài)系統(tǒng)服務(wù)十分重要，它們對(duì)于人類在這個(gè)星球上的可持續(xù)發(fā)展有著決定性的影響。我們必須始終將此牢記在心，即使是在場(chǎng)地尺度的設(shè)計(jì)中也應(yīng)予以貫徹。多環(huán)節(jié)設(shè)計(jì)工作的第一步是在更大尺度范圍下進(jìn)行背景分析。從全球尺度來(lái)看，哈德遜農(nóng)場(chǎng)正位于密西西比—美洲(鳥(niǎo)類)飛行遷徙路線上(圖10)。哈德遜農(nóng)場(chǎng)內(nèi)的森林斑塊、林帶和濕地應(yīng)予以悉心照料，場(chǎng)地開(kāi)發(fā)不應(yīng)使其棲息地發(fā)生損毀或退化，而應(yīng)盡量保持、改善并維護(hù)其在全球遷徙路線中的生態(tài)功能[37]。圖10表明了該場(chǎng)地在國(guó)家尺度乃至全球尺度下的生態(tài)敏感性。從這一宏觀角度出發(fā)，林帶廊道、林地斑塊及濕地棲息地的保護(hù)與整合，在場(chǎng)地分析及總體規(guī)劃階段的重要性不言而喻。場(chǎng)地層面的景觀連通性能反作用于區(qū)域或全球尺度下的連通性。

對(duì)于阿拉巴馬州層面及地區(qū)尺度的更深層次分析也揭示了該場(chǎng)地的生態(tài)重要性，這意味著設(shè)計(jì)團(tuán)隊(duì)在規(guī)劃制定過(guò)程中進(jìn)行整合性決策。只有當(dāng)捍衛(wèi)各自利益的不同人群達(dá)成共識(shí)，同時(shí)又關(guān)注到生物多樣性保護(hù)帶來(lái)的共同長(zhǎng)期利益時(shí)，可持續(xù)發(fā)展才有可能實(shí)現(xiàn)。

本研究以30m的一般距離(缺口小于30m仍視作連接狀態(tài))計(jì)算連通性。然而，景觀連通性評(píng)估更需要以物種為中心的研究方法進(jìn)行[38]。連接結(jié)構(gòu)對(duì)某一物種而言為廊道，但對(duì)另一物種而言則可能是屏障。同時(shí)，棲息地的功能連通性未必需要結(jié)構(gòu)連通性來(lái)保障。某些生物體天生具備越隙能力，能夠跨越完全不宜棲居或局部不宜棲居的基質(zhì)以連接資源；而另外一些物種則無(wú)法越隙，因而需要更高的結(jié)構(gòu)連通性。基于此，連通性研究需要收集物種運(yùn)動(dòng)對(duì)景觀結(jié)構(gòu)的響應(yīng)信息(如穿越不同景觀要素的運(yùn)動(dòng)速度、傳播范圍、傳播期間死亡率和邊界互動(dòng)等)，以及在較大尺度影響作用下，這些響應(yīng)的變化情況。然而，因以物種為基礎(chǔ)的研究極為有限，這類信息往往很難獲取。因此，景觀尺度下的總體連通性評(píng)估只能是根據(jù)現(xiàn)有的不同景觀要素連通性而展開(kāi)的宏觀概論。

盡管關(guān)于生態(tài)系統(tǒng)服務(wù)及生物多樣性保護(hù)已有大量研究，但真正的挑戰(zhàn)來(lái)源于將二者整合于景觀規(guī)劃之中[39-40]。我們需要?jiǎng)?chuàng)新性設(shè)計(jì)工具對(duì)設(shè)計(jì)干預(yù)的影響進(jìn)行實(shí)時(shí)評(píng)估，從而將生態(tài)科學(xué)及設(shè)計(jì)實(shí)踐的優(yōu)勢(shì)更好地結(jié)合并應(yīng)用于可持續(xù)社區(qū)的設(shè)計(jì)中。例如，強(qiáng)調(diào)生物多樣性生態(tài)系統(tǒng)服務(wù)融于生態(tài)重建給人類生計(jì)帶來(lái)的好處，從而獲得更多的公眾支持。進(jìn)行生態(tài)重建，也可對(duì)已處于衰落階段的社區(qū)進(jìn)行再生性設(shè)計(jì)。將人類生計(jì)同環(huán)境管理職責(zé)綜合考慮后，才有可能通過(guò)公眾參與，實(shí)現(xiàn)和諧的設(shè)計(jì)成果。新興的地理設(shè)計(jì)方法[41-42]及生態(tài)智慧理論[43]也為這些問(wèn)題的解決提供了新的視角。

10 全球遷徙路線。哈德遜農(nóng)場(chǎng)位于密西西比—美洲遷徙路線上Global migrating flyway. Hudson Farm is located on the Mississippi-Americas flyway

7 結(jié)語(yǔ)

連通性是景觀生態(tài)學(xué)和景觀設(shè)計(jì)中的一個(gè)重要概念。景觀連通性可用多種方式進(jìn)行量化。FRAGSTATS空間分析模型以GIS數(shù)據(jù)作為輸入層，計(jì)算出連通性及許多其他景觀參數(shù)。在可以獲取GIS數(shù)據(jù)的情況下，這種方法效率較高。通過(guò)比較已有場(chǎng)地和計(jì)劃開(kāi)發(fā)后場(chǎng)地的景觀連通性，能夠得出二者的顯著差異，而這一差異可用于表征項(xiàng)目開(kāi)發(fā)后景觀營(yíng)造的生態(tài)影響，從而避免在實(shí)際城市開(kāi)發(fā)過(guò)程中，對(duì)連通性造成負(fù)面沖擊。事實(shí)上，在總體規(guī)劃制定過(guò)程中也可采取一定措施保持并提升景觀連通性。鑒于眾多大型項(xiàng)目均旨在打造新鎮(zhèn)或新城，上述理念可謂影響深遠(yuǎn)。通過(guò)在設(shè)計(jì)實(shí)施前對(duì)生態(tài)系統(tǒng)服務(wù)進(jìn)行評(píng)估，可選擇最佳或最優(yōu)化設(shè)計(jì)方案以便實(shí)施設(shè)計(jì)干預(yù)。

除此之外，對(duì)于既定地區(qū)的整體生態(tài)系統(tǒng)服務(wù)，需要仔細(xì)評(píng)估，包括根據(jù)不同景觀要素或生態(tài)系統(tǒng)內(nèi)不同物種對(duì)這些服務(wù)加以區(qū)分。要完成這項(xiàng)任務(wù)，我們迫切需要更為先進(jìn)的工具。城市、城市的某些組成部分、幾個(gè)城市作為一個(gè)整體，均可視作“新的生態(tài)系統(tǒng)”，而在這些生態(tài)系統(tǒng)中，生物多樣性及其他生態(tài)系統(tǒng)服務(wù)的價(jià)值不應(yīng)根據(jù)其原先情況來(lái)判斷[44-45]，而應(yīng)根據(jù)其在不斷進(jìn)行的生態(tài)系統(tǒng)演替過(guò)程中生成生態(tài)系統(tǒng)服務(wù)的潛力來(lái)評(píng)定。因此，對(duì)于景觀要素或特定物種對(duì)生物多樣性、人類健康及生態(tài)系統(tǒng)服務(wù)產(chǎn)生的利弊，必須理清其優(yōu)先考慮順序，進(jìn)而指導(dǎo)設(shè)計(jì)干預(yù)。無(wú)論是設(shè)計(jì)和生態(tài)系統(tǒng)間跨尺度的影響－響應(yīng)環(huán)，還是設(shè)計(jì)塑造景觀以及景觀改變?cè)O(shè)計(jì)，相互之間均是不斷作用、不斷增加且共同進(jìn)化的。正如羅伯特·帕克(Robert E. Park)在80多年前所表述的：“城市和城市環(huán)境，是人類遵循自己心意改造其居住的世界所做出過(guò)的最持久、也可說(shuō)是最成功的嘗試。但如果說(shuō)城市是人類創(chuàng)造的世界，那么它也是人類注定要生活的世界。因此，在未能清晰認(rèn)識(shí)這一創(chuàng)造任務(wù)本質(zhì)的情況下，人類在創(chuàng)造城市的同時(shí)其實(shí)也間接地改造了自己。[46]”

注釋：

①圖1、3、4、6、8、9為作者自繪；圖2為作者拍攝；圖5來(lái)自： Dramstad 等, 1996；圖7來(lái)自：FRAGSTATS程序界面；圖10來(lái)自：聯(lián)合國(guó)環(huán)境項(xiàng)目，2006。

②表1來(lái)自：FRAGSTATS程序界面；表2為作者自繪。

致謝：

感謝哈德森項(xiàng)目團(tuán)隊(duì)Chad Adams，F(xiàn)ranklin Collins，Carol Collins，Nick Murray，Nick Koncinja，F(xiàn)rost Rollins，F(xiàn)itz Hudson，Nan Hudson，Jeff Speck等，沒(méi)有他們的熱情幫助本研究就無(wú)法實(shí)現(xiàn)。特別感謝Jack Williams，Michael Robinson和Charlene LeBleu教授，他們自項(xiàng)目伊始的鼓勵(lì)與關(guān)切一直陪伴著我完成了這項(xiàng)研究。最特別需要感謝的是我們優(yōu)秀的合作伙伴Joao Xavier。同時(shí)還要感謝內(nèi)布拉斯加大學(xué)林肯分校的Richard Sutton教授，無(wú)私地分享了他關(guān)于林帶的研究。本文的早期版本發(fā)表于2010年在巴黎召開(kāi)的國(guó)際地理信息系統(tǒng)大會(huì)，在此也向當(dāng)時(shí)對(duì)此研究提出問(wèn)題及給出建議的與會(huì)學(xué)者們表示感謝。

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(編輯/張希)

1 Introduction

The concept of 'landscape connectivity' was introduced to emphasize the interaction between species' attributes and landscape structure in determining movement of organisms among habitat patches[1]. Human activities such as agricultural development, commercial afforestation, infrastructure construction and urbanization have led to habitat fragmentation, namely, loss of the original habitat, reduction in habitat patch size and isolation of habitat patches, and decreasing landscape connectivity[2]. Numerous scientific studies continue to ignore key elements of the original concept while many practical land development projects claim efforts are taken to enhance landscape connectivity. However, without understanding the meaning of landscape connectivity, these studies/projects might actually diminish its potential utility for land management and the conservation of biodiversity. As originally defined by[3], landscape connectivity is 'the degree to which the landscape facilitates or impedes movement among resource patches'. This definition emphasizes that the types, amounts and arrangements of habitat or land use on the landscape influence movement and population dynamics and community structure. However, landscape connectivity should combine twofold of meaning: the description of the physical structure of the landscape (structural connectivity) with special species' response to that structure (functional connectivity), which forms the theoretical background of applying landscape connectivity principles in the practices of landscape planning and design. In this study, a GIS-based approach is used to quantify landscape connectivity. Furthermore, a residential development project in the southern United States was used to explore the meaning of landscape connectivity and its application in town planning.

Ecosystem services have been defined as the benefits that people obtain, either directly or indirectly, from various ecosystems, such as benefits provided by the biodiversity of the nature for humans comprising, for example, food, fiber, climate and regulation, pollination and aesthetic values enhancing well-being of various groups of people[4]. Population growth, urbanization and associated exploitation of natural resources have led to the widespread degradation approximately 60% of the world's ecosystem services[4]. The unsustainable nature of the modern life style and the public perception of ecosystem services must be drastically changed in order to reverse this trend. Thus it is crucial to raise public awareness of the value of ecosystem services and goods, and make them understand how ecosystems function to provide these services. Landscape and urban planning practitioners must also recognise that humans, urban or rural, are only one of the species inhabiting the earth, must abandon their attitude that ecosystem services are taken for granted, and engage in activities to preserve ecosystems in order for them to maintain sustainable provision of ecosystem services.

Biodiversity has many definitions and multiple measures. It can be defined as 'the diversity of life on Earth'[4], and it is always regarded as 'a regulator of underpinning ecosystem processes, as a final ecosystem service and as a good'[5]. Biodiversity is arguably the most important ecosystem services. The conservation of biodiversity can be achieved at different spatial scales. At the global or regional level, the 2011 Convention on Biological Diversity established the Aichi biodiversity targets— a set of goals and targets put in place to protect and promote global biodiversity. Target 11 calls for 17% of terrestrial area (not including Antarctica) to be conserved and protected, specifically those areas where biodiversity is threatened. This equals 22.94 million km2, or an area roughly equal to the size of Canada, China, and India combined[6]. The large scale long term vision for biodiversity conservation is important, but the actions to implement biodiversity conservation or protection can only be achieved at local or site scale. At the site level, biodiversity is significantly influenced by land use, such as agricultural development[7]. It is related to four factors that influence habitat quality: the relative impact of each threat, the relative sensitivity of each habitat to each threat, the distance between the sources of threats and the habitats, and the degree to which the land use is legally protected, and threats are sometimes human-dominated landscapes, such as cropland and urban areas[8].In this study, site level design interventions are investigated in relation to habitat connectivity and biodiversity conservation.

2 Case Study Project Site

2.1 Hedgerow

The vast rural landscape in the southern United States is conspicuously characterized by the hedgerow trees or groves. Hedgerow's primary function in the landscape is to serve as limits, marking boundaries and borders. But hedgerows can also provide products for human in his pursue of food, clothes and shelters, among many other ecosystem services it provides in the rural landscape. The improvement of the visual quality, authenticity of the rural landscape is another important function of hedgerow. Many of the functions of hedgerow can be assessed in the relationship one another[9-13]. However, the most important function of hedgerows in biological conservation is that they are important habitat for wildlife such as bird, mouse, butterfly, etc. Meanwhile, hedgerows functioning as ecological corridors maintain and increase the connectivity of the landscape, maintaining the ecological variability, thus protect and improve the biodiversity of the landscape[14-18].

The patchwork landscape of fields surrounded by high hedgerows is a traditional and familiar feature of the American countryside. Hedgerows are in effect linear strips of trees, groves, or woodlands, which are often critical habitats for wildlife and important for the visual quality of the landscape. The Hudson Farm project was used as the case study to demonstrate how landscape connectivity can be quantified. Hudson Farm is located right on the Black Belt, which is a region of the southeastern U.S. Originally the term describes the prairies and dark soil of central Alabama and northeast Mississippi; however, it has long been used to describe a broad region in the American South characterized by a high percentage of African Americans. It is regarded that the Black Belt covers large areas of Central Georgia, North Florida, Western Mississippi, South Central Alabama, East Central Louisiana, Eastern North Carolina and Southeastern Virginia. Hudson Farm is right located on the black belt, a suburb to the southeast of Montgomery, the capital city of the state of Alabama (Fig. 1). The landscape of Hudson Farm is remarkably characterized by the hedgerow trees or groves. The hedgerows form a series of network of patchwork, creating a landscape of low fields surrounded by high corridors in the form of hedgerow trees and groves.

Hedgerows and woodland are important habitat for wildlife such as bird, bee, mouse, butterfly, etc. (Fig. 2)Meanwhile, the woodland functioning as ecological patch and hedgerows as ecological corridors complement each other in maintaining the diversity of habitat type and connectivity in the landscape. The patch-corridor-matrix formed by hedgerows and woodlands are important to protect and promote biodiversity at the site level in this case. As green infrastructure on site, hedgerow corridors and woodland patches not only give a strong sense of place in the rural landscape but also invite an intimate emotional association with the American countryside[19-20]. Therefore, they must be carefully considered and thoughtfully integrated into the land development project– through ecological landscape planning and innovative urban design strategies.

2.2 Topography

The site was remarkably characterized by a ridgeline that divides the property into several sub-watersheds (Fig. 3). The highest point on the site is located at the lower part of the property, which is 310 feet, and the lowest point of the site is located in the upper part of the property, which is 227 feet. The Hudson farm is a slightly rolling pasture and savannah landscape.

The GIS slope analysis indicates that the site is generally flat, large portion of the land has a maximum slope of 7% (Fig. 3). The slope aspect analysis shows that to below the ridgeline, the site is mostly west- or southwest- facing, while on the upper side of the site, most of the land are north- or northeast- facing (Fig. 3). The slope aspect analysis is for considering the sun pattern, the potential of using solar energy as an alternative energy source.

3 Landscape Connectivity

3.1 Structural Connectivity

Common usage of the term 'connectivity' generally emphasizes the structural aspect, where landscape connectivity is simply equated with linear features of the landscape that promote dispersal, such as physically connected linear corridors. This connectivity allows route from A to B. In a network system (Fig. 4), if there are more alternative routes to travel from A to B, then the network is considered more connected, or it has higher connectivity.

3.2 Functional Connectivity

Physical connectivity is measured by the numbers of loops present in the network. However, in landscape ecology, commonly employed measures of connectivity focus not only on physically connected linear corridor, but also on patch area and how inter-patch distances affect movement in between; i.e. corridors not physically connected, for instance, the stepping stones that can be used by certain species as connected corridor (Fig. 5). This can be called as functional connectivity[21].

Width and connectivity are the primary controls on the five major functions of corridors, i.e., habitat, conduit, filter, source, and sink[9,22-23]. The effect of a gap in corridor on movement of a species depends on length of the gap relative to the scale of species movement, and contrast between the corridor and the gap. However, a row of stepping stones (small patches) is intermediate in connectivity between a corridor and no corridor, and hence intermediate in providing for movement of interior species between patches (Fig. 5a). For highly visually-oriented species, the effective distance for movement between stepping stones is determined by the ability to see each successive stepping stone (Fig. 5b). Loss of one small patch, which functions as a stepping stone for movement between other patches, normally inhibits movement and thereby increases patch isolation (Fig. 5c). The optimal spatial arrangement of a cluster of stepping stones between large patches provides alternate or redundant routes, while maintaining an overall linearly-oriented array between the large patches[30]. This structure facilitates wildlife movements as evidenced by many studies[21-22,24-32].

3.3 Habitat Connectivity

Hudson Farm is a family-owned 2,200 acre property at the suburb of Montgomery, Alabama. The land was used primarily for cattle grazing or hay harvesting. Landscape elements such as trees, hollows, hedgerows, barns, and fences serve as unique landmarks in the Montgomery urban-rural interface. A deep knowledge and understanding of the site will serve as the foundation for planning and design. The preservation and enhancement of distinctive landmarks such as trees, hollows, hedgerows, barns, and fences will maintain the site's unique character. The development of the property is to create a new community with pedestrian-oriented, compact, and mixed-use neighborhoods, in contrast to the single-use conventional suburban development. Creating whole neighborhoods and towns, rather than pockets of suburban development, is a vital step towards creating a sustainable development footprint[33].

On Hudson Farm, hedgerows exist in the landscape in the form of corridor (Fig. 6) and are considered important habitat for biodiversity. Before development, Hudson Farm is used for cattle grazing and hay harvesting. The aerial photography of Hudson Farm area shows the landscape structure of the site (Fig. 6a). Hudson farm is surrounded by large stream corridors and wetlands, which provide critical wildlife habitats for migrating birds and other wildlife. The landscape elements that make Hudson Farm unique are big patches of forests, open fields, corridors in the form of hedgerows, large 'landscape rooms' enclosed by high hedgerows. The hedgerows and tress on the farm enhance the sense of place by providing refreshing long views across the open field dotted or enclosed by high hedgerow trees and groves (Fig. 6b).

4 Quantifiying Connectivity at Landscape Scale

There are various approaches to quantifying landscape connectivity. For example, connectivity (con) is calculated through the a simple equation using numbers of linkages and nodes based on Forman’s urban ecological perspective[9]

con = L / 3 (V-2) (1)

Where

L = number of linkages;

V = number of nodes

However, this approach may be easy to use at a very fine scale where landscape linkages nodes are easily identified. At landscape scale, where the site condition is highly diversified and complicated (e.g. with different forms of connectivity), a new method based on GIS is needed to quantify connectivity.

4.1 GIS-based Landscape Metrics

Many GIS-based landscape metrics are developed by landscape ecologist and scientists and provided for public use[34]. FRAGSTATS is one of these applications designed to compute a wide variety of landscape metrics (including landscape connectivity) for categorical map patterns. This program is developed by the Landscape Ecology Lab at the University of Massachusetts. The original software (version 2) was released in the public domain during 1995 in association with the publication of a USDA Forest Service General Technical Report[5]. This study used the version 3.3 in calculation, which is available for download at the lab's website. FRAGSTATS calculate connectivity based on connectivity metrics (Tab. 1).

For example, the Connectivity Index (con) is calculated as

Where

Cijk= joining between patch j and k (0 = unjoined, 1 = joined) of the same patch type, based on a user-specified threshold distance.

ni= number of patches in the landscape of each patch type i.

In this matrix, connectivity equals the number of functional joining between all patches of the same patch type (sum of Cijkwhere Cijk= 0 if patch j and k are not within the specified distance of each other and Cijk= 1 if patch j and k are within the specified distance), divided by the total number of possible joining between all patches of the same type, multiplied by 100 to convert to a percentage. Therefore the connectivity ranges between 0 and 100. Connectivity = 0 when either the landscape consists of a single patch, or all classes consist of a single patch, or none of the patches in the landscape are connected (i.e., within the userspecified threshold distance of another patch of the same type). Connectivity = 100 when every patch in the landscape is connected[34].

4.2 Input Data and Model Parameterization

The FRAGSTATS spatial pattern analysis program requires GIS data to be prepared in a recognizable file as input to the program to calculate the landscape metrics using FRAGSTATS. The program has to be properly parameterized before it can be run to produce the output statistics (Fig. 7). Details about the FRAGSTATS program, input data preparation, model parameterization, and output data format are available at the program's website.

4.3 Case Study: Hudson Farm

Maintaining networks of corridors is a principle in the design of functional and healthy landscape so as to allow wildlife movement through the landscape and enhance biodiversity. During the master plan making process of the Hudson project, hedgerows are connected, with a continuous tree cover. This concept is generally advocated by many landscape ecologists[35]. This network is superimposed on the ditch network and based on the existing hedgerows. Its spatial arrangement is related to historical factors, such as landlord-worker relationship[36]. Based on this idea, the existing hedgerows are studied (Fig. 8).

To increase connectivity, new hedgerows are proposed to connect the existing hedgerow to create a hedgerow network. The network is meant to be green infrastructure network or ecological infrastructure network which will have both designed functions and ecological functions. Basic ideas are to show why they should be connected and how should they be connected. The left diagram (Fig. 8a) shows the existing hedgerow, the diagram in the middle (Fig. 8b), the red color area, shows the proposed hedgerows. The diagram on the right (Fig. 8c) shows the overlay of existing hedgerow and the proposed hedgerow.

5 Results

Through integrating existing green infrastructure with newly proposed hedgerow corridors, the landscape connectivity has been improved 40% (Tab. 2), according to results from the FRASTATS spatial patter analysis program. The proposed hedgerows are located in existing farm land boundaries, abandoned farm facility sites, and across grazing field to chain up existing remnant trees and groves to form connected hedgerow networks. Therefore the 40% increase of connectivity is achieved without losing much of the core habitat in the form of current large landscape patches. The proposed hedgerows reconnect the broken corridors and increase the overall landscape connectivity dramatically. This indicates the importance of maintaining the intactness of the landscape and its natural vegetation corridor.

The analysis demonstrated that FRAGSTATS can be combined with GIS to calculate connectivity and other parameters at landscape scale. However, the results in Table 2 must be interpreted with caution. For instance, connectivity is measure in 'CONNECT' and 'COHENSION' (Tab. 1-2); even the overall 'CONNCET' as measured use Equation (2) is increased by 40.7%, however, the landscape 'COHENSION’ does not increase as the same magnitude. On the contrary, it decreases slightly[34]. This example illustrates that design interventions can change the ecology of the site; therefore, design intervention must be informed by appropriate evaluation of the consequences following the implementation of the design. This is becoming increasingly easier thanks to the advancement of digital technologies.

6 Discussion

The conservation of biodiversity and related ecosystem services are a global challenge. It needs systematic approaches that work across time and spatial scales. Biodiversity planning requires design capability that addresses these complexities. A scaled system thinking approach is used to further interpret habitat connectivity and biodiversity conservation at global and regional scales[36]. Ecosystem science research has demonstrated the need for multi-scale analysis that takes into consideration the scale and resolution of inputs, and of the processes being evaluated. In landscape planning, scale thinking is to examine interactions in the land systems across site level, local level, regional level, national level, and even global level (Fig. 9). Scale thinking is essential to gain a holistic perspective of the site and its broader context, understand of these very forces that are simultaneously functioning at other scales, and relate these cross-scale functions to gain a holistic view of boarder interrelated landscape processes and their potential influences on the design solution.

Biodiversity and related ecosystem services are important issues that have critical influence on the human sustainability on this planet. This notion must always be kept in mind even when designing at the site scale. The first step in these chained design efforts is to conduct context analysis and broader scales. Hudson Farm is right located on the Mississippi Americas Flyway (Fig.10). The forest patches, hedgerows and wetlands within Hudson Farm should receive careful consideration where development should not eliminate or degrade these habitats but maintain or improve them in order to keep its ecological function in the global flyway[37]. The image serves as strong arguments that the site is ecologically sensitive, not only at the national scale, but also at the global level. With these bigpicture images in mind, it is easily understood why the conservation and integration of hedgerow corridors, woodland patches, and wetland habitats are so important in the site analysis and master planning phases. Landscape connectivity at site level forms augmented connectivity at regional or global scale.

Further analysis at the Alabama state level and local scale also reveals the ecological significance of the site, which requires the design team to exercise integrated decision making in the plan-making process. Sustainable development is only possible when consensus is reached among different groups defending their own interests without neglecting the commonlong-term benefits of biodiversity conservation and preservation.

In this study, a general distance of 30m (a gap below this distance is still considered connected) is used to calculate the connectivity. However, assessing landscape connectivity requires a species-centered approach[38]. A connected structure may serve as a corridor for one species, but a barrier for another. Meanwhile, habitat does not necessarily need to be structurally connected to be functionally connected. Some organisms, by virtue of their gap-crossing abilities, are capable of linking resources across an uninhabitable or partially inhabitable matrix, while other species cannot cross gaps therefore requires higher structure connectivity. Therefore, the study of connectivity requires information on species' movement responses to landscape structure (e.g., movement rates through different landscape elements, dispersal range, mortality during dispersal, boundary interactions, etc.) and how those responses differ as a function of broader-scale influences. Such information is typically quite difficult to obtain, as very limited study is carried out on a species to species basis. Therefore, the assessment of the overall connectivity at landscape scale is but a big-picture overview of the connectivity of different landscape elements present.

Despite numerous studies on ecosystem services and biodiversity conservation, challenges still remain in integrating ecosystem services and biodiversity conservation into landscape planning[39-40]. New innovative design tools that enable real-time assessment of the impact of design intervention are needed so that the strength of ecological sciences and design practices can be combined for designing sustainable community. For example, the integration of biodiversity ecosystem services into ecological restoration offers an opportunity to enhance public support by emphasizing its benefits to human livelihood. The approach of ecological restoration may take form of the regenerative design of a community that had been undergoing a decay process. A harmonious design outcome may be achieved through engaging the public considering both human livelihood and environmental stewardship. The emerging geodesign approach[41-42]and ecowisdom theories[43]provide new insights to these questions.

7 Conclusion Remarks

Connectivity is an important concept in landscape ecology and landscape architecture. Landscape connectivity can be measured in different ways. FRAGSTATS spatial analysis model uses use GIS data as input layers to calculate connectivity along with many other landscape parameters. This is efficient when GIS data are available. Significant difference when comparing the landscape connectivity of the existing site with that of proposed development can be easily used to assess the impact of the modified landscape after proposed development, thus negative impacts on connectivity can be avoid in real urban development projects. Instead, measures can be taken to maintain and improve landscape connectivity during the master plan making process. The impact of this notion is profound considering the nature of the large projects alike aiming at creating new towns or cities. Pre-implementation ecosystem services evaluation can be done to inform design intervention through optimization or selecting the most capable design solution.

In addition, the overall ecosystem services for a given region should be carefully evaluated, including differentiating the services by different landscape components, or different species in the ecosystems. More advanced tools capable of completing this task are highly demanded. The sustainability of city of some components of cities or even some cities as a whole may be viewed as "novel ecosystems" in which the value of biodiversity and other ecosystem services should not be judged by its origins[44-45]but by its potential to produce ecosystem services in the ongoing process of ecosystem succession. Therefore, priorities around whether alandscape component or certain species are producing benefits or harm to biodiversity, human health, and ecosystem services must be organised and used to guide design intervention. The influence-response loop between design and ecosystem across scales, or the interplay between shaping landscape through design and design being shaped by the landscape, is mutual, incremental, and coevolutionary. This is similar to what Robert E. Park said more than 80 years ago: "For the city and the urban environment represent man's most consistent and, on the whole, his most successful attempt to remake the world he lives in more after his heart's desire. But if the city is the world which man created, it is the world in which he is henceforth condemned to live. Thus, indirectly, and without any clear sense of the nature of his task, in making the city man has remade himself"[46].

Acknowledgment

The author wish to thank the Hudson project team for their kind help that makes this study possible: Chad Adams, Franklin and Carol Collins, Nick Murray, Nick Koncinja, Frost Rollins, Fitz Hudson, Nan Hudson, Jeff Speck, etc. Special thanks go to Professors Jack Williams, Michael Robinson and Charlene LeBleu whose encouraging words from the very beginning of the project have longlasting effects on this work. The most special thanks go to Joao Xavier, thanks very much for being a nice working partner. The author also wishes to thank Professor Richard Sutton in the University of Nebraska-Lincoln for sharing with the author his research and publications on hedgerow. An early version of this paper has been presented at the 2012 International Conference in GIS in Paris and the author wish to thank the conference participants who asked questions or offered comments on this study.

Integrating Landscape Connectivity into Town Planning for Biodiversity Ecosystem Service Provision

Biodiversity is one of the most important ecosystem services in the wake of increasing extinction rate of endangered species worldwide. Biodiversity conservation is critical in maintaining the viability of ecosystems at local, regional, and global scales. Landscape connectivity combines a description of the physical structure of the landscape with special species' response to that structure, which forms the theoretical background of applying landscape connectivity principles in landscape planning practices, particularly for these environmentally progressive projects that integrate provision for ecosystem services. In this paper, an eco-town development project in the southeastern United States was used as a case study to explore design considerations that promote landscape connectivity and facilitate biodiversity conservation. Based on geographic information system (GIS) and spatial statistical analysis (FRAGSTATS), this study attempts to quantify the landscape connectivity characterized by woodlands and hedgerows in southeastern United States where substantial areas with natural landscape are being urbanized due to the ever expanding real estate industry and high demand for new residential development. Results suggest that adding new hedgerows to the existing green infrastructure on site can significantly increase landscape connectivity thus improve ecosystem services due to the increase of habitat size and increased connectivity among habitat patches. In conclusion, this study shed lights on how to balance the needs of new urban development and eco-services provision by maintaining a higher level of landscape connectivity, thus will inform the design intervention aimed at achieving not only livability but also sustainability.

landscape architecture; landscape connectivity; ecosystem services; biodiversity conservation; landscape planning

TU986

A

1673-1530(2017)01-0066-16

10.14085/j.fjyl.2017.01.0066.16

2016-12-16

上海市浦江人才計(jì)劃(15PJC092)；國(guó)家自然青年科學(xué)基金項(xiàng)目(51508391)

Fund Items: Swppooted by Shanghai Pujiang Program(Grant No. 15PJC092); National Natural Science Foundation (Youth Foundation) (Grant No. 51508391) are acknowledged.

(澳)陳思清/1973年生/男/湖北人/澳大利亞墨爾本大學(xué)設(shè)計(jì)學(xué)院高級(jí)講師/博士生導(dǎo)師/澳大利亞TDG地理設(shè)計(jì)工作室創(chuàng)始人 / 美國(guó)奧本大學(xué)景觀建筑碩士/中國(guó)科學(xué)院地理信息系統(tǒng)博士/主要從事生態(tài)城景觀規(guī)劃、地理設(shè)計(jì)、彈性城市和綠色基礎(chǔ)設(shè)施等方面的教學(xué)、研究和實(shí)踐工作(VIC 3010) Authors：

CHEN Siqing was born in Hubei in 1973. He is a Senior Lecturer, doctoral supervisor in Melbourne School of Design, The University of Melbourne, Australia. He is the founding director of the TGD GeoDesign Studio in Australia. He holds a Master of Landscape Architecture from Auburn University and a PhD of GIS from Chinese Academy of Sciences. His research, teaching and practice areas includes ecotown landscape planning, geodesign, resilient city and green infrastructure (VIC 3010).汪潔瓊/1981年生/女/上海人/同濟(jì)大學(xué)建筑與城市規(guī)劃學(xué)院景觀學(xué)系/同濟(jì)大學(xué)建筑與城市規(guī)劃學(xué)院生態(tài)智慧與城鄉(xiāng)生態(tài)實(shí)踐研究中心/高密度人居環(huán)境生態(tài)與節(jié)能教育部重點(diǎn)實(shí)驗(yàn)室/講師、系主任助理(研究生教學(xué))、碩士生導(dǎo)師、澳大利亞墨爾本大學(xué)博士、助教/研究方向?yàn)樯鷳B(tài)系統(tǒng)服務(wù)與空間形態(tài)機(jī)制、水生態(tài)、綠色基礎(chǔ)設(shè)施等領(lǐng)域的教學(xué)、科研和工程實(shí)踐(上海200092)

WANG Jie-qiong was born in Shanghai in 1981. She is a lecturer, postgraduate supervisor and also a Department Director Assistant in the College of Architecture and Urban Planning, Tongji University. She holds a PhD from The University of Melbourne and was a tutor and guest lecturer there. As a research member of the Center for Ecological Wisdom and Practice Research and the Key Laboratory of Ecology and Energy-saving Study of Dense Habitat (Tongji University), her research focuses on the ecosystem services and physical form, water ecology, green infrastructure (Shanghai 200092).譯者簡(jiǎn)介：

王南/1984 年生/女/江蘇南京人/同濟(jì)大學(xué)環(huán)境科學(xué)與工程學(xué)院在讀博士后/同濟(jì)大學(xué)建筑與城市規(guī)劃學(xué)院景觀學(xué)系專業(yè)博士/研究方向?yàn)榫坝^規(guī)劃與設(shè)計(jì)理論與方法(上海200092) Translator：

WANG Nan was born in 1984 in Nanjing, Jiangsu

Province. She is a post-doctoral candidate of College of Environmental Science and Engineering, Tongji University. She holds a PhD of Landscape Architecture from College of Architecture and Urban Planning, Tongji University. Her research focuses on theories and methodology of landscape planning and design (Shanghai 200092).

修回日期：2017-01-23