郭金停,韓風(fēng)林,布仁倉(cāng),胡遠(yuǎn)滿,馬 俊,聶志文,朱菊蘭,任百慧

1 中國(guó)科學(xué)院沈陽(yáng)應(yīng)用生態(tài)研究所,森林與土壤生態(tài)國(guó)家重點(diǎn)實(shí)驗(yàn)室,沈陽(yáng) 110016 2 中國(guó)科學(xué)院大學(xué),北京 100049 3 沈陽(yáng)師范大學(xué),沈陽(yáng) 110034

大興安嶺北坡多年凍土區(qū)植物群落分類及其物種多樣性對(duì)凍土融深變化的響應(yīng)

郭金停1,2,韓風(fēng)林1,2,布仁倉(cāng)1,*,胡遠(yuǎn)滿1,馬 俊1,2,聶志文1,2,朱菊蘭3,任百慧1,2

1 中國(guó)科學(xué)院沈陽(yáng)應(yīng)用生態(tài)研究所,森林與土壤生態(tài)國(guó)家重點(diǎn)實(shí)驗(yàn)室,沈陽(yáng) 110016 2 中國(guó)科學(xué)院大學(xué),北京 100049 3 沈陽(yáng)師范大學(xué),沈陽(yáng) 110034

氣候變化背景下凍土環(huán)境對(duì)地上植物群落的影響備受關(guān)注。鑒于此,選擇了大興安嶺北坡作為研究區(qū),應(yīng)用雙向指示種分析(TWINSPAN)和典范對(duì)應(yīng)分析法(CCA)對(duì)大興安嶺北坡不同凍土融深的30個(gè)樣地進(jìn)行了群落分類,分析了物種多樣性對(duì)凍土融深的響應(yīng)。結(jié)果表明,1)研究區(qū)30個(gè)溝谷凍土樣地植物群落可劃分為3個(gè)群叢組,TWINSPAN的分類結(jié)果很好的反映了群叢組的分布與凍土融深的關(guān)系,即隨著凍土融深由淺變深,群落由柴樺(Betulafruticosa)+狹葉杜香(Ledumpalustrevar.angustum)-苔草(Carexsubpediformis)群叢組逐漸過(guò)渡到柴樺(Betulafruticosa)-苔草(Carexsubpediformis)群叢組和柴樺(Betulafruticosa)+細(xì)葉沼柳(Salixrosmarinifolia)-苔草(Carexsubpediformis)群叢組,并在CCA二維排序圖上得到了驗(yàn)證；2)地上植物群落的物種多樣性指數(shù)隨著凍土融深的增加表現(xiàn)出先上升后下降的單峰變化趨勢(shì)；在50cm

大興安嶺北坡；凍土融深；物種多樣性；TWINSPAN ；CCA

高寒生態(tài)系統(tǒng)是高寒環(huán)境下多年凍土的凍融交替作用發(fā)展起來(lái)的一種特殊生態(tài)系統(tǒng)[1],多年凍土的發(fā)育程度是維持其生態(tài)平衡的物質(zhì)基礎(chǔ)。大興安嶺位于歐亞大陸多年凍土帶南緣,也是我國(guó)多年凍土的發(fā)育地之一,具有地溫高、凍土厚度淺、熱穩(wěn)定性差、對(duì)氣候變暖的反應(yīng)十分敏感等特點(diǎn)[2- 3]。由于氣候變暖,大興安嶺多年凍土正在由南向北逐步消退[4- 5],主要表現(xiàn)為最大季節(jié)融化深度增大、凍土厚度減薄、地溫升高、融區(qū)擴(kuò)大以及多年島狀凍土消失等[6]。這種變化將對(duì)區(qū)域生態(tài)系統(tǒng)產(chǎn)生巨大影響,主要表現(xiàn)為植物群落結(jié)構(gòu)、物種多樣性以及物種分布等諸多結(jié)構(gòu)和生態(tài)功能發(fā)生不同程度的變化[7-9],并由此導(dǎo)致高寒生態(tài)系統(tǒng)消退加速[10- 12],繼而對(duì)整個(gè)生態(tài)系統(tǒng)產(chǎn)生影響[13- 14]。因此認(rèn)清植物群落對(duì)凍土融深變化的響應(yīng)特征是研究大興安嶺凍土區(qū)植被恢復(fù)和物種多樣性保護(hù)的首要工作。

迄今為止,對(duì)大興安嶺凍土的研究多局限于凍土分布、凍土的退化模擬、資源保護(hù)等[15- 18],而關(guān)于物種多樣性對(duì)凍土融深變化響應(yīng)的研究尚見(jiàn)報(bào)道。為此,本文應(yīng)用雙向指示種分析法(TWINSPAN)和典范對(duì)應(yīng)分析法(CCA),對(duì)大興安嶺北坡凍土區(qū)的30個(gè)植被群落進(jìn)行了排序和分類,并分析了群落變化的主要影響因子以及物種多樣性對(duì)凍土融深的變化規(guī)律,旨在為凍土退化及其對(duì)全球變化的響應(yīng)研究提供理論基礎(chǔ)。

1 研究地區(qū)與研究方法

1.1 研究區(qū)的自然概況

研究區(qū)地處大興安嶺北坡(50°01′01″—53°26′25″N,119°07′02″—121°49′17″E),海拔620—960m。該地區(qū)屬寒溫帶大陸性季風(fēng)氣候,冬季嚴(yán)寒而漫長(zhǎng),年均氣溫-4—-1℃,年均降水量350—550mm,無(wú)霜期80—100d。研究樣地位于草地生態(tài)系統(tǒng)與森林生態(tài)系統(tǒng)的過(guò)渡帶,物種組成較為豐富,多數(shù)物種屬于寒溫帶物種,少數(shù)屬于溫帶物種；植物群落的垂直結(jié)構(gòu)比較簡(jiǎn)單,成層現(xiàn)象明顯,分別由喬木層、灌木層、草本層和地被層四個(gè)層次組成。其中喬木層由興安落葉松(Larixgmelinii)老頭林和少量白樺(Betulaplatyphylla)組成；灌木層物種較多,其中柴樺(Betulafruticosa)、狹葉杜香(Ledumpalustrevar.angustum)、篤斯越桔(Vacciniumuliginosum)等為凍土植被群落的特征種；草本層物種最多,其中苔草(Carexsubpediformis)等為草本層的優(yōu)勢(shì)種；地被層主要由中位泥炭蘚和白齒泥炭蘚等各種泥炭蘚所覆蓋[19]；土壤類型主要是草甸土和沼澤土,有機(jī)質(zhì)含量較高,水分、養(yǎng)分豐富,土質(zhì)較疏松,地表有積水[20]。

1.2 樣方調(diào)查

2014年7月,采用系統(tǒng)取樣方法,在研究區(qū)內(nèi)選擇基本相似生境條件下的30塊樣地進(jìn)行調(diào)查(表1)。每個(gè)樣地隨機(jī)設(shè)置2m×2m灌木樣方6個(gè),1m×1m草本樣方9—12個(gè),以確保每個(gè)樣地90%的物種被調(diào)查到。對(duì)于高度小于2m或胸徑小于2.5cm的喬木,作為灌木調(diào)查。在每個(gè)樣方中記錄植物種的名稱、多度、蓋度、高度等數(shù)量指標(biāo),以及樣地所在的經(jīng)度、緯度、海拔高度、坡度、坡向、凍土融深等環(huán)境因子,并對(duì)每個(gè)樣地活動(dòng)層進(jìn)行了土壤采樣。

表1 調(diào)查樣地基本情況

“—”代表在0—150cm范圍內(nèi)沒(méi)有挖到凍土

1.3 研究方法

1.3.1 地理數(shù)據(jù)的獲取

通過(guò)GPS獲取每個(gè)樣點(diǎn)的經(jīng)度、緯度、海拔高度、坡度(表1)。

1.3.2 土壤數(shù)據(jù)的獲取

將取土樣放置烘箱,烘至恒重,土壤水分中自由態(tài)水以蒸汽形式全部散失掉,再稱重量從而獲得土壤含水量。采用直接挖深法獲得每個(gè)樣點(diǎn)的凍土融深(表1)。

1.3.3 群落分類

采用雙向指示種分析法(TWINSPAN)和典范對(duì)應(yīng)分析法(CCA)[21],對(duì)大興安嶺北坡30個(gè)溝谷凍土濕地的植物群落進(jìn)行數(shù)量分類和排序分析,將凍土植被群落分成3個(gè)群叢組,兩種方法分別用國(guó)際通用軟件WinTWINS 2.3和CANOCO for Windows 4.5完成,并對(duì)群落變化的影響因子進(jìn)行分析,所用軟件為R 3.0.2vegan程序包。

1.3.4 不同群叢組物種組成分析

以重要值(IV)表示物種在3個(gè)群叢組的綜合型數(shù)量指標(biāo),其計(jì)算公式如下：

IV=(相對(duì)高度+相對(duì)蓋度+相對(duì)頻度)/3

1.3.5 物種多樣性對(duì)凍土融深的響應(yīng)分析

數(shù)據(jù)分析時(shí)將每個(gè)群叢組的若干樣方的調(diào)查結(jié)果進(jìn)行平均,選擇能反應(yīng)群叢組狀況的多樣性指數(shù),采用Patrick豐富度指數(shù)、Simpson多樣性指數(shù)、Shannon-Wiener多樣性指數(shù)、Pielou均勻度指數(shù)[22],指數(shù)計(jì)算公式如下：

Patrick豐富度指數(shù)

R=S

Simpson多樣性指數(shù)

Shannon-Wiener多樣性指數(shù)

Pielou均勻度指數(shù)：

2 結(jié)果與分析

2.1 大興安嶺北坡凍土植被群落的TWINSPAN分類和CCA排序

應(yīng)用TWINSPAN分類和CCA排序?qū)Υ笈d安嶺北坡凍土植被群落30個(gè)樣地進(jìn)行了群落分類,結(jié)果顯示,根據(jù)凍土融深由淺到深,研究區(qū)群落可分為3個(gè)群叢組,群從組的定義以及群落的分類原則和系統(tǒng),這3個(gè)組分別代表3個(gè)植物群叢組,即植物群從組Ⅰ、Ⅱ、Ⅲ(Ⅰ柴樺+狹葉杜香-苔草群叢組、Ⅱ柴樺-苔草群叢組、Ⅲ柴樺+細(xì)葉沼柳-苔草群叢組)(圖1)。

由分類結(jié)果顯示,凍土融深(PMD)和海拔高度(Alt)、坡度(Slo)有線性正相關(guān)關(guān)系,與土壤含水量(SWC)有線性負(fù)相關(guān)關(guān)系(圖1)。4個(gè)排序軸的特征值分別為0.487、0.376、0322和-0.433,CCA排序結(jié)果圖能很好地反應(yīng)3個(gè)群叢組與環(huán)境的關(guān)系,在凍土融深由淺到深的連續(xù)變化上,群落組也由群叢組Ⅰ逐漸變化到群叢組Ⅱ和群叢組Ⅲ(圖1)。

研究結(jié)果顯示,土壤含水量隨凍土融深的增加呈現(xiàn)出明顯的降低趨勢(shì),土壤含水量(SWC)與凍土融深(PMD)之間存在明顯的負(fù)相關(guān)關(guān)系(R2=0.74,P<0.01)(圖1)。

研究結(jié)果顯示,凍土融深(PMD)、地形和土壤含水量3個(gè)因子對(duì)群落變化的解釋率為38%,其中地形因子、凍土融深(PMD)和土壤含水量三者的綜合效應(yīng)為群落變化的最大解釋因子(圖2),除凍土融深、地形和土壤含水量以外還有其它因素也影響群落的變化,還有待于進(jìn)一步研究。

圖1 研究區(qū)凍土植物群落的CCA二維排序圖Fig.1 Two-dimensional CCA ordination diagram of plant communities in the study area

圖2 不同環(huán)境因素對(duì)群落變化的解釋率Fig.2 Different environmental factors on the interpretation of the community change rate

2.2 不同群叢組物種組成分析

植物群叢組Ⅰ為柴樺+狹葉杜香-苔草群叢組。該群叢組主要分布于凍土融深為0—50cm范圍內(nèi),屬于凍土融深較淺的群落類型。灌木層以柴樺和狹葉杜香為優(yōu)勢(shì)種,其蓋度分別為30%—45%和15%—60%,并伴有篤斯越桔和興安落葉松等伴生種；草本層以白毛羊胡子草和大葉樟等作為優(yōu)勢(shì)種,并伴有三葉鹿藥、北懸鉤子、草問(wèn)荊等伴生種(表2)。

表2 研究區(qū)各群叢組中優(yōu)勢(shì)種和主要伴生種重要值

*P<0.05；#：優(yōu)勢(shì)種或共優(yōu)種；同行數(shù)據(jù)后不同字母表示差異顯著(P<0.05)

植物群叢組Ⅱ?yàn)椴駱?苔草群叢組。該群叢組主要分布于凍土融深為50—150cm范圍內(nèi),屬于凍土融深較深的群落類型。灌木層以柴樺、篤斯越桔和柳葉繡線菊為優(yōu)勢(shì)種,且狹葉杜香為主要伴生種,除此以外還有細(xì)葉沼柳和小葉杜鵑等；草本叢除群叢組Ⅰ的伴生種外還有野古草、五脈山黧豆和北方拉拉藤等伴生種。

植物群叢組Ⅲ為柴樺+細(xì)葉沼柳-苔草群叢組。該群叢組主要分布于凍土融深大于150cm范圍內(nèi),屬于島狀凍土的群落類型。灌木層以柴樺、細(xì)葉沼柳為優(yōu)勢(shì)種,且篤斯越桔和金老梅等為主要伴生種,除此以外還有越桔柳和五蕊柳等；草本叢以大穗苔草大葉樟、苔草等為優(yōu)勢(shì)種并伴有五脈山黧豆、草問(wèn)荊、小白花地榆、北方拉拉藤等伴生種。

2.3 物種多樣性對(duì)凍土融深的響應(yīng)

Patrick指數(shù)與凍土融深具有顯著的相關(guān)性(R2=0.58,P<0.01)。PMD≤50cm時(shí),物種種類較為豐富,物種數(shù)為23.83±2.44；50cm150cm時(shí),物種數(shù)急劇下降至21.14±1.57。Pielou指數(shù)和Shannon-Wiener指數(shù)隨凍土融深的增加出現(xiàn)先升高后降低的趨勢(shì),且50cm150cm兩指數(shù)差異不顯著。Simpson指數(shù)與凍土融深在PMD≤50cm和50cm150cm時(shí)物種的豐富度和多樣性指數(shù)較低,且差異顯著(圖3)。

圖3 不同活動(dòng)層埋深下物種多樣性的變化Fig.3 Variations of plant species diversities with different depths of active layer of permafrost

3 討論

3.1 大興安嶺北坡多年凍土區(qū)植物群落的TWINSPAN分類和CCA排序

本文運(yùn)用了TWINSPAN分類和CCA排序?qū)⑷郝浞譃?個(gè)群叢組并得到了相互驗(yàn)證。由圖1、圖2和圖3可以看出：在景觀尺度范圍內(nèi),海拔高度及坡度均是凍土發(fā)育的地形條件,地勢(shì)較低的平緩地帶是凍土發(fā)育的客觀條件,凍土融深的大小也會(huì)直接影響到土壤含水量,融深較淺的土壤含水量較高[23- 25],凍土融深由淺到深群叢組也由Ⅰ柴樺+狹葉杜香-苔草群叢組逐漸過(guò)渡到Ⅱ柴樺-苔草群叢組和Ⅲ柴樺+細(xì)葉沼柳-苔草群叢組,該分類結(jié)果較客觀的反映了植物群落類型的分布與環(huán)境因子的關(guān)系。3個(gè)群叢組間的明顯過(guò)渡表明群落類型對(duì)生境的變化規(guī)律有顯著地響應(yīng),由以上的4個(gè)因素差異造成了凍土區(qū)不同群叢組的群落組成存在一定的間斷性。

3.2 氣候變化情境下凍土群落變化

群叢組Ⅰ、群叢組Ⅱ和群叢組Ⅲ分別代表3個(gè)不同的群叢組,不同的群叢組所對(duì)應(yīng)的凍土融深范圍也不相同,隨著凍土融深由淺變深,部分物種的重要值明顯減小,如狹葉杜香、白毛羊胡子草、大葉樟等；另外一些物種的重要值明顯增加,如柴樺、細(xì)葉沼柳等；隨著凍土融深的增加,一些在凍土融深較淺的環(huán)境下不存在的物種也相繼出現(xiàn),如野古草、五脈山黧豆、北方拉拉藤、地榆、東北羊角芹、馬藺、二歧銀蓮花、和裂葉蒿等。氣候變化情境下,凍土融深由淺變深甚至部分島狀凍土消失,由空間序列代替時(shí)間序列,群落也由群叢組Ⅰ逐漸變化到群叢組Ⅱ和群叢組Ⅲ。

3.3 物種多樣性對(duì)凍土融深的響應(yīng)

目前就多樣性與生境之間的關(guān)系已有大量報(bào)道,研究表明物種多樣性與生境條件密不可分[26-29]。更有學(xué)者對(duì)生境條件對(duì)物種多樣性影響進(jìn)行了總結(jié)和綜述[30- 33],指出了土壤水熱條件對(duì)物種多樣性有重要的作用,本研究發(fā)現(xiàn),凍土的不同發(fā)育程度對(duì)土壤含水量有直接的影響,凍土融深小于50cm時(shí)土壤含水量較大,由于植物根系無(wú)法汲取土壤水分導(dǎo)致物種多樣性指數(shù)較小,隨著凍土融深的增加50cm150cm時(shí)土壤含水量較小,此時(shí)水分成為物種多樣性指數(shù)下降的限制因子。因此,多年凍土區(qū)凍土融化是土壤水的重要來(lái)源,物種多樣性隨凍土融深的變化趨勢(shì)實(shí)則是土壤含水量隨凍土融深的變化趨勢(shì)。多年凍土區(qū)影響物種多樣性的因子有很多,非生物因子也非常重要[34- 36]。

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Classification of plant communities and species diversity responses to changes in the permafrost depths of the north slope of the Great Khingan Mountain valley of Northeast China

GUO Jinting1,2,HAN Fenglin1,2,BU Rencang1,*,HU Yuanman1, MA Jun1,2,NIE Zhiwen1,2, ZHU Julan3,REN Baihui1,2

1StateKeyLaboratoryofForestandSoilEcology,InstituteofAppliedEcology,ChineseAcademyofSciences,Shenyang110016,China2UniversityofChineseAcademyofSciences,Beijing100049,China3Shenyangnormaluniversity,Shenyang110034,China

The Great Khingan Mountains, located in northeastern China, feature zonal permafrost. Lying on the southern edge of the Eurasian permafrost boundary, the permafrost region of the northeast portion of the Great Khingan Mountains is one of the plant communities most sensitive to the effects of global warming. Permafrost is gradually degrading from south to north, because of the effects of human activity and environmental changes such as global warming. The degradation of permafrost leads to changes in the characteristics of permafrost plant communities, such as species composition, species diversity, and biomass. The impacts of permafrost on vegetation have become a key research topic in the field of climate change research. However, previous studies of permafrost have mostly focused on the distribution of permafrost, and so the mechanistic connection between permafrost and environmental factors, and the impacts of permafrost degradation on community composition and structure have not been the focus of much quantitative research. Thus, the plant communities of 30 plots on the north slope of the Great Khingan Mountains were classified according to permafrost depth, using two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA). Accordingly, the effects of permafrost depth on plant species diversity were analyzed using these plots. The results indicate the following. (1) Plant communities were categorized into three plant associations, and as the permafrost depths changed along a gradient from shallow to deep, plant associations changed fromBetulafruticose+Ledumpalustrevar.angustum-CarexsubpediformistoBetulafruticosa-CarexsubpediformisandBetulafruticosa+Salixrosmarinifolia-Carexsubpediformis. These relationships were validated by CCA ordination. In addition, permafrost melting depth (PMD), topography, and soil moisture could together explain 38% of the community change. Their combined effect was the biggest explanatory factor for community change. (2) The species diversity index increased trend initially (in shallow permafrost) and decreased as the permafrost melting depth increased. It reached its maximum value at about 50—150 cm deep. When PMD ≤ 50 cm and PMD > 150 cm, the species richness and diversity index are low, and the significant difference. Patrick index and melting permafrost depth has significant correlation (R2= 0.58, P < 0.58). When PMD ≤ 50 cm, the species richness of the communities was higher, at 23.83±2.44; when 50 < PMD ≥ 150 cm, it was 26.36±2.01; and when PMD > 150 cm, it fell sharply to 21.14±1.57. The Pielou index and Shannon-Wiener index with the increase of the permafrost melts deep appeared a trend of reducing the rise, and when 50150 cm. This study provides a theoretical basis for the prediction of trends in the variation of plant community composition after the degradation of permafrost. It is also important for the development and implementation of agriculture and forestry in permafrost areas. In addition, it would be an effective guide for forest management and biodiversity conservation efforts in permafrost regions.

The Great Khingan Mountains；permafrost deeps；species diversity；TWINSPAN；CCA

國(guó)家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃(2013CBA01807)；中國(guó)科學(xué)院先導(dǎo)專項(xiàng)(XDA05050200)；國(guó)家自然科學(xué)基金項(xiàng)目(41371198)

2015- 04- 30;

日期:2016- 03- 02

10.5846/stxb201504300895

*通訊作者Corresponding author.E-mail: burc@iae.ac.cn

郭金停,韓風(fēng)林,布仁倉(cāng),胡遠(yuǎn)滿,馬俊,聶志文,朱菊蘭,任百慧.大興安嶺北坡多年凍土區(qū)植物群落分類及其物種多樣性對(duì)凍土融深變化的響應(yīng).生態(tài)學(xué)報(bào),2016,36(21):6834- 6841.

Guo J T,Han F L,Bu R C,Hu Y M, Ma J,Nie Z W, Zhu J L,Ren B H.Classification of plant communities and species diversity responses to changes in the permafrost depths of the north slope of the Great Khingan Mountain valley of Northeast China.Acta Ecologica Sinica,2016,36(21):6834- 6841.