西藏草地植物功能性狀與多項(xiàng)生態(tài)系統(tǒng)服務(wù)關(guān)系

潘 影, 余成群,2, 土艷麗, 孫 維,2, 羅黎鳴, 苗彥軍, 武俊喜,2,*

1 中國(guó)科學(xué)院地理科學(xué)與資源研究所, 北京 100101 2 中國(guó)科學(xué)院地理科學(xué)與資源研究所生態(tài)系統(tǒng)網(wǎng)絡(luò)觀測(cè)與模擬重點(diǎn)實(shí)驗(yàn)室, 北京 100101 3 西藏自治區(qū)高原生物研究所, 拉薩 850001 4 西藏大學(xué)農(nóng)牧學(xué)院, 林芝 860000

西藏草地植物功能性狀與多項(xiàng)生態(tài)系統(tǒng)服務(wù)關(guān)系

潘 影1, 余成群1,2, 土艷麗3, 孫 維1,2, 羅黎鳴2,4, 苗彥軍4, 武俊喜1,2,*

1 中國(guó)科學(xué)院地理科學(xué)與資源研究所, 北京 100101 2 中國(guó)科學(xué)院地理科學(xué)與資源研究所生態(tài)系統(tǒng)網(wǎng)絡(luò)觀測(cè)與模擬重點(diǎn)實(shí)驗(yàn)室, 北京 100101 3 西藏自治區(qū)高原生物研究所, 拉薩 850001 4 西藏大學(xué)農(nóng)牧學(xué)院, 林芝 860000

針對(duì)植被功能性狀與生態(tài)系統(tǒng)服務(wù)功能之間的相互關(guān)系，構(gòu)建了西藏草地株高和可食性兩種功能性狀的9項(xiàng)指標(biāo)，并基于土壤和植物采樣，分析了9項(xiàng)植物功能性狀指標(biāo)和5項(xiàng)生態(tài)系統(tǒng)服務(wù)指標(biāo)間的相關(guān)性，探討了4種機(jī)制(Mass ratio, Selection, Niche complementarity及Insurance)在西藏草地的適用性。結(jié)果表明，9項(xiàng)功能性狀指標(biāo)中，株高Rao和可食種與所有種株高CWM比分別與土壤有機(jī)碳、土壤全氮和土壤含水率3項(xiàng)生態(tài)系統(tǒng)服務(wù)指標(biāo)呈顯著負(fù)相關(guān)及顯著正相關(guān)。說(shuō)明群落植被對(duì)光能競(jìng)爭(zhēng)的互補(bǔ)性及可食性狀植株在群落中的光能資源相對(duì)競(jìng)爭(zhēng)力，與土壤固碳、肥力供給及水源涵養(yǎng)有顯著相關(guān)關(guān)系。而群落可食種、優(yōu)勢(shì)種、優(yōu)勢(shì)種與次優(yōu)勢(shì)種對(duì)光能資源競(jìng)爭(zhēng)力水平，可食植株多樣性、可食植株在群落中的優(yōu)勢(shì)度及其光能資源競(jìng)爭(zhēng)力均值，對(duì)草地生態(tài)系統(tǒng)服務(wù)無(wú)顯著影響。西藏草地植物功能性狀對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)的影響機(jī)制從光能資源競(jìng)爭(zhēng)角度更符合Niche complementarity和Insurance理論，而從可食功能性狀角度更符合Mass ratio和Selection理論。

西藏; 植物功能性狀; 生態(tài)系統(tǒng)服務(wù); 機(jī)理

植物與環(huán)境相互作用的漫長(zhǎng)進(jìn)化過(guò)程，形成了植物多樣性；這些多樣性改變了生態(tài)系統(tǒng)的過(guò)程與功能，影響著生態(tài)系統(tǒng)服務(wù)[1-4]。研究表明，生物多樣性對(duì)生態(tài)系統(tǒng)功能與服務(wù)的影響多由植物性狀的變化引起；這些植物性狀也被稱為植物功能性狀[5-6]。植物功能性狀對(duì)生態(tài)系統(tǒng)功能與服務(wù)影響的基礎(chǔ)研究在土地利用、氣候變化對(duì)生態(tài)系統(tǒng)功能與服務(wù)影響的模擬[7-9]以及生態(tài)規(guī)劃及區(qū)域評(píng)價(jià)中都有所應(yīng)用[10-13]。

國(guó)際上針對(duì)植物功能性狀對(duì)生態(tài)系統(tǒng)功能與服務(wù)的影響提出了幾種理論，包括Mass ratio, Selection, Niche complementarity及Insurance[6]。Mass ratio理論最早針對(duì)功能性狀及多樣性對(duì)生態(tài)系統(tǒng)初級(jí)生產(chǎn)力影響的研究[14]，后擴(kuò)展到生態(tài)系統(tǒng)功能[6]。Mass ratio理論認(rèn)為在某個(gè)特定時(shí)間斷面，生態(tài)系統(tǒng)功能主要由其優(yōu)勢(shì)種功能性狀決定，而與次優(yōu)勢(shì)種和一些生物量較小物種無(wú)關(guān)[6,14]。Selection理論與Mass ratio大體一致，表示生態(tài)系統(tǒng)功能主要由群落中生物量最大的優(yōu)勢(shì)種的功能性狀決定，與其他生物量較小物種無(wú)關(guān)[15]。

而Niche complementarity理論是指群落中不同生態(tài)位植物能夠增強(qiáng)群落的資源利用率，從而提高群落生物量，影響生態(tài)系統(tǒng)功能[15]。而Insurance理論表示，在群落中，一些非優(yōu)勢(shì)種，甚至稀有種，能夠在群落的生態(tài)系統(tǒng)功能供給方面提供“緩沖”作用，緩沖降雨、溫度、病原體等生物、環(huán)境因子變化對(duì)群落生態(tài)功能的影響[16]。

4種理論在不同區(qū)域、不同生態(tài)系統(tǒng)有不同適用性，對(duì)這種適用性的研究有助于理解當(dāng)?shù)貧夂颦h(huán)境因子-植物群落-生態(tài)系統(tǒng)功能服務(wù)的相互聯(lián)系和影響，指導(dǎo)當(dāng)?shù)厣鷳B(tài)系統(tǒng)恢復(fù)及生態(tài)系統(tǒng)功能與服務(wù)提升[17-19]。本文擬利用西藏草地土壤、植被采樣數(shù)據(jù)，研究西藏草地植物典型功能性狀對(duì)草地多功能的影響及四種理論的適用性。

1 研究地區(qū)和研究方法

1.1 研究區(qū)概況

新倉(cāng)村(29°29′—30°02′N、91°15′—91°41′E)隸屬于西藏自治區(qū)拉薩市達(dá)孜縣，位于拉薩河流域的藏南谷地下游南岸。研究區(qū)域平均海拔4500 m，年均溫7.5 ℃，年均日照時(shí)數(shù)3065 h，年均降水450 mm，降水多集中在植物生長(zhǎng)季6—9月。采樣區(qū)域土壤類型包括亞高山草甸草原土、亞高山灌叢草甸土、高山草甸土，植被類型包括亞高山草甸草原、亞高山灌叢草甸、高山草甸。

1.2 研究方法

本文選取株高及可食性兩種功能性狀，分析其功能性狀差異性和功能性狀均值[6]。在此基礎(chǔ)上構(gòu)建了9項(xiàng)指標(biāo)(表1)，其中群落株高功能性狀差異性、可食性功能性狀差異性參數(shù)反映植株功能性狀在群落生態(tài)位的多樣性，用以驗(yàn)證niche complementarity及insurance理論在西藏草地的適用性。所有種、優(yōu)勢(shì)及次優(yōu)勢(shì)種株高功能性狀均值及可食性功能性狀優(yōu)勢(shì)度用于分析優(yōu)勢(shì)種、次優(yōu)勢(shì)種等與多功能的相關(guān)性，用以驗(yàn)證mass ratio和selection理論在西藏草地的適用性。本文選取了地上可食生物量、土壤有機(jī)碳、土壤全氮、土壤含水率、植被覆蓋度5項(xiàng)指標(biāo)定量生態(tài)系統(tǒng)服務(wù)，研究不同功能性狀指標(biāo)與生態(tài)系統(tǒng)服務(wù)之間的關(guān)系。具體參數(shù)見表1。

表1 植物功能性狀對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)影響機(jī)制分析參數(shù)

功能性狀差異性由Rao指數(shù)定量，計(jì)算公式如下：

(1)

式中,s為群落中物種數(shù)，pi、pj為第i、j個(gè)物種在群落種的相對(duì)蓋度，dij為物種i和j之間某種性狀的差額。

功能性狀均值由CWM指數(shù)定量，計(jì)算公式如下：

(2)

式中,s為群落中物種數(shù)，pi為第i個(gè)物種在群落種的相對(duì)蓋度，di為物種i功能性狀值。

1.3 數(shù)據(jù)來(lái)源

本文數(shù)據(jù)樣品于2012年7月采集于西藏拉薩市達(dá)孜縣新倉(cāng)村山坡草地，海拔梯度從3949 m至4940 m，沿坡底到坡頂共設(shè)15個(gè)5 m× 5m樣地，每個(gè)樣地中隨機(jī)選取3個(gè)面積為0.5 m×0.5 m的樣方重復(fù)。物種的株高、蓋度和多度現(xiàn)場(chǎng)記錄，地上生物量齊地面分種刈割，于實(shí)驗(yàn)室65 ℃烘干48 h稱重[20-21]。并在刈割后的樣方挖剖面環(huán)刀取土，測(cè)定含水量，土鉆取土測(cè)定有機(jī)碳、全氮。本文的植株可食性是針對(duì)牦牛、山羊、綿羊及馬，假設(shè)一種或一種以上牲畜采食該種草，則該草可食。為了減少牲畜啃食對(duì)植株高度的影響，在測(cè)量植株高度時(shí)，僅選取葉片完整的植株進(jìn)行測(cè)量。

2 研究結(jié)果

2.1 西藏草地植物功能性狀的相互聯(lián)系

在株高與可食性兩個(gè)功能性狀的9項(xiàng)指標(biāo)中，有6項(xiàng)指數(shù)相互呈顯著相關(guān)(圖1)。其中所有種、優(yōu)勢(shì)種、優(yōu)勢(shì)種與次優(yōu)勢(shì)種株高CWM指標(biāo)兩兩之間呈顯著正相關(guān)；說(shuō)明某群落優(yōu)勢(shì)種和次優(yōu)勢(shì)種對(duì)光能資源競(jìng)爭(zhēng)力越強(qiáng)，整個(gè)群落光能資源競(jìng)爭(zhēng)水平越高。

圖1 草地植物功能性狀指數(shù)皮爾遜相關(guān)性Fig.1 Pearson correlation of the pairs of indicators of the plant functional traits點(diǎn)圖為散點(diǎn)圖，數(shù)字為皮爾遜相關(guān)系數(shù)，其中**代表在0.01水平顯著相關(guān)

株高Rao指數(shù)和可食種與所有種株高CWM比指標(biāo)呈顯著負(fù)相關(guān)；說(shuō)明可食性物種在群落中對(duì)光能資源競(jìng)爭(zhēng)力越高，群落植物對(duì)光能資源競(jìng)爭(zhēng)互補(bǔ)性越低，或者說(shuō)群落株高功能性狀趨同。

可食性種CWM分別與所有種、優(yōu)勢(shì)種、優(yōu)勢(shì)種與次優(yōu)勢(shì)種株高CWM呈顯著正相關(guān)關(guān)系；主要由于新倉(cāng)村草地群落大部分由可食性種建群。

可食性種的豐富度與株高相關(guān)指標(biāo)無(wú)顯著相關(guān)關(guān)系，說(shuō)明群落可食性功能性狀的差異性與群落植株對(duì)光能資源競(jìng)爭(zhēng)力無(wú)明顯關(guān)系。

2.2 西藏草地植物功能性狀與多項(xiàng)生態(tài)系統(tǒng)服務(wù)的相互影響關(guān)系

9項(xiàng)植物功能性狀指標(biāo)中，株高Rao、可食種與所有種株高CWM比兩項(xiàng)指標(biāo)與土壤有機(jī)碳、土壤全氮和土壤含水率3項(xiàng)生態(tài)系統(tǒng)服務(wù)指標(biāo)顯著相關(guān)(圖2,表2)。其中株高Rao與土壤有機(jī)碳、土壤全氮、土壤含水率呈顯著負(fù)相關(guān)，說(shuō)明群落植被對(duì)光能競(jìng)爭(zhēng)互補(bǔ)性越強(qiáng)，則對(duì)土壤中養(yǎng)分、水分等資源有更多利用，導(dǎo)致土壤有機(jī)碳、全氮和含水率的降低。

圖2 植物功能性狀指標(biāo)與生態(tài)系統(tǒng)服務(wù)指標(biāo)散點(diǎn)圖Fig.2 Scatter diagrams of the plant functional traits and ecosystem services

可食種與所有種株高CWM比和土壤有機(jī)碳、土壤全氮、土壤含水率呈顯著正相關(guān)，說(shuō)明具有可食性狀植株在群落中的光能資源相對(duì)競(jìng)爭(zhēng)力，與土壤有機(jī)碳、全氮和含水量的保持有顯著正相關(guān)關(guān)系。

所有種、優(yōu)勢(shì)種、優(yōu)勢(shì)種與次優(yōu)勢(shì)種、可食種株高CWM，可食種豐富度、可食種占總種比例、可食生物量比例7項(xiàng)指標(biāo)與生態(tài)系統(tǒng)服務(wù)的5項(xiàng)指標(biāo)皆無(wú)顯著相關(guān)關(guān)系。說(shuō)明群落植株包括可食種、優(yōu)勢(shì)種、優(yōu)勢(shì)種與次優(yōu)勢(shì)種對(duì)光能資源競(jìng)爭(zhēng)力水平，具有可食性狀植株的多樣性、具有可食性狀植株在群落中的優(yōu)勢(shì)度和其光能資源競(jìng)爭(zhēng)力均值，對(duì)草地生態(tài)系統(tǒng)服務(wù)無(wú)顯著影響。

表2 植物功能性狀指標(biāo)與生態(tài)系統(tǒng)服務(wù)指標(biāo)皮爾遜相關(guān)性

3 討論

3.1 植物功能性狀指標(biāo)和生態(tài)系統(tǒng)服務(wù)指標(biāo)選取

本文選取了株高和可食性兩項(xiàng)植物功能性狀，株高是反映植株對(duì)光能資源的競(jìng)爭(zhēng)力較成熟的指標(biāo)[6-7,12-13]，同樣比葉面積和葉片氮含量也能反映植株光能資源競(jìng)爭(zhēng)力[5,7]。由于研究區(qū)域和問(wèn)題的不同，可食性性狀在很多國(guó)際研究中被忽視[5,22-23]，但由于西藏當(dāng)?shù)啬撩竦纳a(chǎn)生活和其生態(tài)安全屏障功能同樣重要[24]，可食性功能性狀在西藏草地研究中尤為值得關(guān)注。除了株高和可食性兩種功能性狀外，還有很多功能性狀，如葉片磷含量、葉片光合速率、植株生殖高度、根密度、凋落物碳氮含量等，可以反映群落的健康水平、繁殖能力、碳氮等營(yíng)養(yǎng)物質(zhì)循環(huán)[5,25-26]。這些功能性狀都與生態(tài)系統(tǒng)服務(wù)相關(guān)[27]。生態(tài)系統(tǒng)水源涵養(yǎng)功能與水循環(huán)過(guò)程有關(guān)，其中地表植被、枯落物層及土壤的最大持水力、土壤的降雨入滲率、地表蒸散率等都是重要參數(shù)。草地土壤持水占草地生態(tài)系統(tǒng)持水的大部分，而小尺度上，本研究選取的土壤含水率可以反映一定時(shí)間斷面水循環(huán)的狀態(tài)，從一定程度上區(qū)別不同生態(tài)系統(tǒng)水源涵養(yǎng)功能。

3.2 西藏草地植物功能性狀對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)的影響機(jī)制理論

Mass ratio, Selection理論和Niche complementarity及Insurance理論的較大分歧點(diǎn)是在群落中的一些非優(yōu)勢(shì)種和稀有種對(duì)生態(tài)系統(tǒng)功能是否有影響。

本研究結(jié)果表明，株高功能性狀差異性對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)有顯著影響，而無(wú)論是優(yōu)勢(shì)種、次優(yōu)勢(shì)種或全部種的株高性狀均值對(duì)生態(tài)系統(tǒng)服務(wù)皆無(wú)顯著影響。這意味著，西藏草地生態(tài)系統(tǒng)服務(wù)與植株株高差異程度有關(guān)，而與優(yōu)勢(shì)種或次優(yōu)勢(shì)種等的株高功能性狀相對(duì)水平無(wú)關(guān)。本研究結(jié)果表明，西藏草地從光能資源競(jìng)爭(zhēng)角度，其植物功能性狀對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)的影響更加符合Niche complementarity和Insurance理論。

而西藏草地可食性功能性狀對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)的影響機(jī)制與株高性狀不同。可食性功能性狀的指標(biāo)更多程度上反映的是群落中可食種與不可食種的種間競(jìng)爭(zhēng)和對(duì)環(huán)境的適應(yīng)性。本研究結(jié)果表明，在反映可食性功能性狀優(yōu)勢(shì)度與生態(tài)系統(tǒng)服務(wù)聯(lián)系方面，可食種與所有種株高CWM較豐富度比例、生物量比例更加適合本研究?？墒承苑N的優(yōu)勢(shì)度，或更進(jìn)一步描述，是可食性種在群落中對(duì)光能的競(jìng)爭(zhēng)力與草地生態(tài)系統(tǒng)服務(wù)顯著相關(guān)。而可食性種間的多樣性或株高差異性對(duì)生態(tài)系統(tǒng)服務(wù)并無(wú)顯著影響。西藏草地可食功能性狀對(duì)多項(xiàng)生態(tài)系統(tǒng)服務(wù)的影響更加符合Mass ratio和Selection理論。

4 結(jié)論

本文利用株高、可食性兩個(gè)植物功能性狀的9項(xiàng)指標(biāo)與5項(xiàng)生態(tài)系統(tǒng)服務(wù)指標(biāo)的統(tǒng)計(jì)分析，能夠較好反映西藏草地植物功能性狀與多項(xiàng)生態(tài)系統(tǒng)服務(wù)的相關(guān)性；同樣也初步印證了Mass ratio, Selection, Niche complementarity及Insurance理論在西藏草地生態(tài)系統(tǒng)的適用性。對(duì)于可食性功能性狀，前兩種理論更加適用，而對(duì)于株高功能性狀后兩種理論更加適用。結(jié)果表明，西藏植株光能競(jìng)爭(zhēng)的生態(tài)位差異及可食性種優(yōu)勢(shì)度與草地生態(tài)系統(tǒng)服務(wù)供給顯著相關(guān)，而群落優(yōu)勢(shì)種、次優(yōu)勢(shì)種等的光能競(jìng)爭(zhēng)水平及可食性種多樣性與草地生態(tài)系統(tǒng)服務(wù)供給無(wú)關(guān)。

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The relationship between plant functional traits and multiple ecosystem services in a Tibetan grassland ecosystem

PAN Ying1, YU Chengqun1,2, TU Yanli3, SUN Wei1,2, LUO Limimg2,4, MIAO Yanjun4, WU Junxi1,2,*

1InstituteofGeographicSciencesandNaturalResourcesResearch,ChineseAcademyofSciences,Beijing100101,China2KeyLaboratoryofEcosystemNetworkObservationandModeling,InstituteofGeographicSciencesandNaturalResourcesResearch,ChineseAcademyofSciences.Beijing100101,China3TibetPlateauInstituteofBiology,Lhasa850001,China4AgriculturalandAnimalHusbandryCollegeofTibetUniversity,Linzhi860000,China

We studied the relationships among plant functional traits and multiple ecosystem services. Nine indicators of plant functional traits of plant heights and palatability were established, which were Rao index of plant heights, the community weighted mean value (CWM) of plant heights of all species, the CWM of plant heights of dominant species, the CWM of plant heights of dominant and subdominant species, the richness of palatable plants, the richness ratio of palatable species to all species, the ratio of palatable biomass to total biomass, the CWM of plant heights of palatable species, and the CWM of the ratio of heights of palatable plants to all plant species. The ecosystem services we analyzed included forage supply, soil carbon stocks, soil fertilization supply, water regulation, and soil retention. Further, we attempted to test four candidate mechanisms by which plant functional traits influence ecosystem services. These were:1) mass ratio, 2) selection, 3) niche complementarity, and 4) insurance. In 2012, we collected soil and vegetation samples from Xincang village, Lhasa, Tibet. Ecosystem services and plant functional traits were quantified based on these samplings. Pearson correlations were calculated among the nine functional traits, as well as between the functional traits and ecosystem services. The results showed that among the functional traits, the Rao index of plant heights was significant negatively correlated with soil organic carbon, soil total nitrogen, and soil water content. The ratio of the CWM of the heights of palatable plants to all plant species was significant positively correlated with soil organic carbon, soil total nitrogen, and soil water content. However, the CWM of the plant heights of all species, palatable species, dominant species, dominant and subdominant species, as well as the richness of palatable species, the ratio of the palatable specie richness to all species, and the ratio of palatable biomass to all species, were not significantly correlated with any of the ecosystem services. Our results demonstrated that the niche complementarity of the light captures of the plant community has negative impacts on ecosystem soil carbon stock, fertilization provisioning, and water regulating services. However, the relative niche competitiveness of light captures of palatable plants in the community has positive impacts on ecosystem soil carbon stock, fertilization provisioning, and water regulating services. The results imply, from the perspective of resource competitiveness, the concepts of niche complementarity and insurance best characterize the mechanisms by which plant functional traits determine ecosystem services in grassland. However, from the perspective of palatability, the concepts of mass ratio and selection are more reasonable.

Tibet; plant functional traits; ecosystem services; mechanisms

國(guó)家自然科學(xué)青年基金(31200364); 國(guó)家科技支撐計(jì)劃項(xiàng)目(2011BAD17B05); “西部之光”人才培養(yǎng)計(jì)劃項(xiàng)目(20100309); 西藏生態(tài)專項(xiàng)(Z2012C07G03)

2014-04-16; < class="emphasis_bold">網(wǎng)絡(luò)出版日期:

日期:2014-12-18

10.5846/stxb201404160738

*通訊作者Corresponding author.E-mail: wujx@igsnrr.ac.cn

潘影, 余成群, 土艷麗, 孫維, 羅黎鳴, 苗彥軍, 武俊喜.西藏草地植物功能性狀與多項(xiàng)生態(tài)系統(tǒng)服務(wù)關(guān)系.生態(tài)學(xué)報(bào),2015,35(20):6821-6828.

Pan Y, Yu C Q, Tu Y L, Sun W, Luo L M, Miao Y J, Wu J X.The relationship between plant functional traits and multiple ecosystem services in a Tibetan grassland ecosystem.Acta Ecologica Sinica,2015,35(20):6821-6828.