不同恢復(fù)年限侵蝕紅壤生態(tài)化學(xué)計(jì)量特征

張秋芳,陳奶壽,陳坦,呂茂奎,楊玉盛,謝錦升?

(1.濕潤亞熱帶山地生態(tài)國家重點(diǎn)實(shí)驗(yàn)室培育基地(福建師范大學(xué)),350007,福州; 2.福建師范大學(xué)地理科學(xué)學(xué)院,350007,福州;3.福建師范大學(xué)地理研究所,350007,福州)

不同恢復(fù)年限侵蝕紅壤生態(tài)化學(xué)計(jì)量特征

張秋芳1,2,陳奶壽1,2,陳坦1,2,呂茂奎1,2,楊玉盛1,3,謝錦升1,3?

(1.濕潤亞熱帶山地生態(tài)國家重點(diǎn)實(shí)驗(yàn)室培育基地(福建師范大學(xué)),350007,福州; 2.福建師范大學(xué)地理科學(xué)學(xué)院,350007,福州;3.福建師范大學(xué)地理研究所,350007,福州)

為了解侵蝕紅壤碳、氮、磷分配格局及化學(xué)計(jì)量特征,本文在長汀縣侵蝕紅壤區(qū)選取不同恢復(fù)年限(2、13、30、33年)、立地條件相近、樣地情況基本一致的馬尾松林作為研究對象,以未治理侵蝕地(CK1)和次生林(CK2)為對照,對其土壤總有機(jī)碳、全氮和全磷質(zhì)量分?jǐn)?shù)及其化學(xué)計(jì)量比的特征進(jìn)行測定和分析。結(jié)果表明:1)隨恢復(fù)年限的增加,土壤總有機(jī)碳和全氮質(zhì)量分?jǐn)?shù)呈線性增加,土壤全磷質(zhì)量分?jǐn)?shù)無顯著變化,恢復(fù)2～33 a的馬尾松林土壤總有機(jī)碳、全氮和全磷質(zhì)量分?jǐn)?shù)仍顯著低于CK2土壤,表明土壤肥力的恢復(fù)是一個(gè)漫長的過程。2)土壤C∶N、C∶P、N∶P隨恢復(fù)年限的增加呈上升趨勢,恢復(fù)2～33 a的馬尾松林土壤C∶N逐漸趨向CK2。3)土壤C∶N和C∶P與土壤總有機(jī)碳質(zhì)量分?jǐn)?shù)呈正顯著相關(guān),土壤N∶P與全氮質(zhì)量分?jǐn)?shù)呈顯著正相關(guān),土壤N∶P與全磷質(zhì)量分?jǐn)?shù)相關(guān)性不顯著,表明侵蝕退化紅壤恢復(fù)過程中,土壤化學(xué)計(jì)量比主要受土壤碳和氮質(zhì)量分?jǐn)?shù)的控制,暗示著侵蝕紅壤現(xiàn)階段的植被恢復(fù)對N素的響應(yīng)比對P素的響應(yīng)更敏感。

侵蝕紅壤;生態(tài)恢復(fù);馬尾松林;化學(xué)計(jì)量學(xué)

生態(tài)化學(xué)計(jì)量學(xué)(ecological stoichiometry)是分析元素相互作用、探究生態(tài)系統(tǒng)能量平衡與多種化學(xué)元素(主要是碳、氮、磷)平衡的科學(xué)[1-2]。近年來,許多研究者應(yīng)用生態(tài)化學(xué)計(jì)量學(xué)的原理和方法,針對植物化學(xué)計(jì)量學(xué)的變化開展大量的研究[3-4],而對土壤養(yǎng)分的生態(tài)化學(xué)計(jì)量學(xué)研究則相對較少[5]。土壤是植物生存的物質(zhì)基礎(chǔ)[6],直接影響植被群落的物種組成與生產(chǎn)力[7],尤其土壤中氮、磷元素是限制植物生長發(fā)育的最重要和最大量的元素[8],也是各種蛋白質(zhì)和遺傳物質(zhì)的重要組成元素,氮、磷的循環(huán)限制著生態(tài)系統(tǒng)的大多數(shù)過程;而且,土壤元素的化學(xué)計(jì)量比和平衡影響著植物的生長發(fā)育,如土壤N∶P可以改變植物體N∶P,從而對植物生長產(chǎn)生影響[9]:因此,研究土壤的生態(tài)化學(xué)計(jì)量學(xué)特征,可以揭示土壤養(yǎng)分的可獲得性,對于認(rèn)識(shí)生態(tài)系統(tǒng)C、N、P元素循環(huán)和平衡機(jī)制具有重要意義[10]。

我國南方紅壤面積約203.53萬km2,而水土流失面積高達(dá)60余萬km2,是南方面積最大、墾殖指數(shù)最高、水土流失最嚴(yán)重的區(qū)域,部分地區(qū)曾一度成為南方的“紅色沙漠”[11]。自20世紀(jì)80年代以來,當(dāng)?shù)亻_展大量的水土保持與生態(tài)恢復(fù)實(shí)踐,侵蝕紅壤的恢復(fù)大有成效,如南方典型侵蝕紅壤長汀縣的土壤侵蝕面積顯著下降,治理區(qū)植被覆蓋率由15%～35%提高到65%～91%[12]。隨著植被覆蓋度的增加,侵蝕紅壤有機(jī)質(zhì)、鹽基代換量、全量和有效氮、磷、鉀等質(zhì)量分?jǐn)?shù)均呈增大趨勢[13],土壤保護(hù)性和非保護(hù)性有機(jī)碳庫儲(chǔ)量亦顯著提高[14];但目前少有以時(shí)間序列關(guān)注不同恢復(fù)年限侵蝕紅壤C、N、P元素及其耦合關(guān)系的變化的研究,這限制了對侵蝕紅壤植被恢復(fù)過程元素的平衡和循環(huán)機(jī)制的進(jìn)一步認(rèn)識(shí)。鑒于此,本文于福建省長汀縣侵蝕紅壤區(qū)選取不同恢復(fù)年限(2、13、30、33 a),但立地條件相近、樣地情況基本一致的馬尾松林作為研究對象,以未治理的侵蝕地(CK1)和次生林(CK2)為對照,關(guān)注不同恢復(fù)年限土壤的C、N、P質(zhì)量分?jǐn)?shù)及其化學(xué)計(jì)量狀況,以期揭示侵蝕紅壤不同恢復(fù)年限土壤全量養(yǎng)分N、P及化學(xué)計(jì)量特征,分析N、P養(yǎng)分對植被恢復(fù)的限制性作用,為該區(qū)侵蝕紅壤水土流失治理提供一定的參考。

1 研究區(qū)概況

福建省長汀縣河田鎮(zhèn)(E 116°18＇～116°31＇,N 25°33＇～25°48＇)處于福建省西南部、汀江上游,屬中亞熱帶季風(fēng)氣候區(qū)。年均氣溫17.5～18.8℃,平均無霜期260 d,平均日照時(shí)數(shù)1 925 h,≥10℃積溫4 100～4 650℃,年均降水量約1 737mm。河田鎮(zhèn)屬河谷盆地,海拔300～500m。土壤為中粗粒花崗巖發(fā)育的紅壤,抗蝕能力低。地帶性植被(常綠闊葉林)破壞殆盡,現(xiàn)有植被主要以馬尾松(Pinusmassoniana)次生林和人工林為主。

不同治理時(shí)間的馬尾松林樣地均位于河田鎮(zhèn),土壤母巖均為粗晶花崗巖。其中,以來油坑未治理侵蝕地(CK1)和大路口的次生林(CK2)為對照,不同治理時(shí)間的馬尾松林恢復(fù)前的本底條件與未治理地基本相似。除石壁下治理13 a的馬尾松林偶見少量杉木(Cunninghamia lanceolata)外,CK1和不同恢復(fù)年限的馬尾松林喬木層樹種均為馬尾松,林下植被主要為芒萁(Dicranopteris dichotoma)。大路口的次生林(CK2)是當(dāng)?shù)卮迕駷楸Ｗo(hù)風(fēng)水而得以保存下來的,喬木層樹種主要為馬尾松和木荷(Schima superba),估計(jì)林齡在70～110年左右,林下植被蓋度在95%以上,灌木層主要有小葉赤楠(Syzygium grijsii)、毛冬青(Ilex pubescens)、檵木(Loropetalum chinensis)等,草本層以芒萁為主。樣地概況見表1。

表1　樣地基本概況Tab.1 Basic information of plots

2 研究方法

2.1土樣采集

于2013年8月,對不同恢復(fù)年限的馬尾松林進(jìn)行樣方調(diào)查,即在每個(gè)試驗(yàn)樣地設(shè)3個(gè)20 m×20 m樣方,在樣方內(nèi)對喬木層進(jìn)行每木檢尺,記錄種名、樹高、胸徑、冠幅;在每個(gè)樣方內(nèi)按S形選取5個(gè)樣點(diǎn),用直徑為5 cm土鉆按0～10、10～20 cm土層分層取樣,混合后用自封袋裝好樣品并做好標(biāo)記。

2.2樣品處理與化學(xué)分析

將土壤樣品剔除石礫和草根等雜物,自然風(fēng)干后過2mm土壤篩,再用四分法取1/4樣品過0.149 mm篩,裝瓶保存用于測定土壤總有機(jī)碳、全氮和全磷質(zhì)量分?jǐn)?shù)。用碳氮元素分析儀(Elementar Vario MAX)測定土壤總有機(jī)碳和全氮質(zhì)量分?jǐn)?shù),土壤全磷質(zhì)量分?jǐn)?shù)采用HClO4-H2SO4法提取[15],用流動(dòng)分析儀(Skalar san++)測定。

2.3數(shù)據(jù)處理與分析

采用SPSS 20.0統(tǒng)計(jì)軟件對數(shù)據(jù)進(jìn)行統(tǒng)計(jì)分析,相關(guān)分析采用Person相關(guān)法,應(yīng)用單因素方差分析(One-way ANOVA)和最小顯著差異性(LSD)比較不同恢復(fù)年限馬尾松林土壤C、N、P質(zhì)量分?jǐn)?shù)、不同深度土壤C、N、P質(zhì)量分?jǐn)?shù)及其化學(xué)計(jì)量比的差異(α=0.05),并用Excel 2013制圖。

3 結(jié)果與分析

3.1不同恢復(fù)年限土壤C、N、P質(zhì)量分?jǐn)?shù)

由圖1可知,土壤C、N、P質(zhì)量分?jǐn)?shù)隨恢復(fù)年限的變化速率并不一致,其中0～10 cm土壤C、N質(zhì)量分?jǐn)?shù)隨恢復(fù)年限呈線性增長(R2=0.97、0.86,P＜0.01),土壤P質(zhì)量分?jǐn)?shù)的變化則沒有明顯的規(guī)律性。植被恢復(fù)2～33 a的0～10 cm土壤C、N質(zhì)量分?jǐn)?shù)均顯著高于CK1,分別增加44.3%～788.6%、24.7%～267.4%,但植被恢復(fù)2～33 a土壤C、N質(zhì)量分?jǐn)?shù)仍顯著低于CK2(圖1(a)和(b))。植被恢復(fù)2 a的0～10 cm馬尾松林土壤P質(zhì)量分?jǐn)?shù)與CK1無顯著性差異,恢復(fù)13～33 a的0～10 cm土壤P質(zhì)量分?jǐn)?shù)比CK1增加90.8%～205.2%(圖1(c))。植被恢復(fù)13～33 a的土壤P質(zhì)量分?jǐn)?shù)趨近于CK2(圖1(c))。不同恢復(fù)年限10～20 cm土壤C、N、P質(zhì)量分?jǐn)?shù)顯著低于0～10 cm土壤C、N、P質(zhì)量分?jǐn)?shù)?？傮w而言,植被恢復(fù)過程中0～10 cm土壤C、N增加量明顯,其中,隨著恢復(fù)年限的增加,土壤C質(zhì)量分?jǐn)?shù)的變化最明顯,N質(zhì)量分?jǐn)?shù)變化次之,P質(zhì)量分?jǐn)?shù)變化最小,植被恢復(fù)首先影響0～10 cm土層。

圖1　不同恢復(fù)年限土壤C、N、P質(zhì)量分?jǐn)?shù)變化Fig.1 Changes of C,N,and P contents in soil in different restoration years

3.2不同恢復(fù)年限土壤C∶N、C∶P、N∶P生態(tài)化學(xué)

計(jì)量比的特征

嚴(yán)重侵蝕退化地不僅C、N、P的質(zhì)量分?jǐn)?shù)低,其化學(xué)計(jì)量比也低。由表2可見,隨著恢復(fù)年限的增加,0～10 cm土壤C∶N、C∶P、N∶P呈上升趨勢,尤其0～10 cm土壤C∶P與恢復(fù)時(shí)間呈顯著性線性關(guān)系(R2=0.98,P＜0.05)。植被恢復(fù)2～33 a的馬尾松林0～10 cm土壤C∶N、C∶P、N∶P顯著高于未治理侵蝕地(CK1),分別提高29%～132%、85%～289%、9%～66%,但植被恢復(fù)13 a的馬尾松林0～10 cm土壤N∶P與CK1無顯著性差異。植被恢復(fù)13～30 a的0～10 cm土壤C∶N與CK2無顯著性差異,但恢復(fù)33 a的0～10 cm土壤C∶N相比CK2顯著增加32%;植被恢復(fù)2～33 a的0～10 cm土壤C∶P、N∶P均顯著低于CK2。10～20 cm土壤C∶N、C∶P、N∶P低于0～10 cm土壤的C∶N、C∶P、N∶P,但10～20和0～10 cm土壤的C∶N、C∶P、N∶P的變化趨勢基本一致。

表2　不同恢復(fù)年限的化學(xué)計(jì)量比Tab.2 Stoichiometric ratios in different restoration years

3.3土壤C、N、P質(zhì)量分?jǐn)?shù)與C∶N、C∶P、N∶P化學(xué)計(jì)量比的相關(guān)性

由表3可得:土壤C、N、P的質(zhì)量分?jǐn)?shù)、C∶N、C∶P、N∶P呈極顯著正相關(guān)關(guān)系;土壤N與P質(zhì)量分?jǐn)?shù)、C∶P、N∶P呈極顯著正相關(guān)關(guān)系,但是土壤N質(zhì)量分?jǐn)?shù)與C∶N無顯著相關(guān)關(guān)系;土壤P質(zhì)量分?jǐn)?shù)與C∶N呈極顯著正相關(guān)關(guān)系,但與C∶P、N∶P無顯著相關(guān)關(guān)系。

表3　土壤C、N、P質(zhì)量分?jǐn)?shù)與C∶N∶P化學(xué)計(jì)量比的相關(guān)性Tab.3 CorrelationbetweensoilC,N,andPcontentsand stoichiometricratios

4 討論

4.1不同恢復(fù)年限馬尾松林土壤碳、氮、磷質(zhì)量分?jǐn)?shù)特征

土壤C、N、P是土壤養(yǎng)分的重要組成部分,與土壤肥力、植物營養(yǎng)有效性相關(guān),影響植物生產(chǎn)力,是反映土壤質(zhì)量的重要指標(biāo)[16]。本研究中,不同恢復(fù)年限馬尾松林0～20 cm土壤C、N、P質(zhì)量分?jǐn)?shù)變化范圍分別為1.25～21.32、0.18～1.38、0.04～0.12 g/kg,與福建省0～20 cm紅壤平均C、N質(zhì)量分?jǐn)?shù)(分別是(22.10±1.84)、(1.49±0.08)g/kg)[17]及亞熱帶未侵蝕紅壤P質(zhì)量分?jǐn)?shù)(如米櫧次生林0～20 cm土壤全磷質(zhì)量分?jǐn)?shù)為0.15 g/kg)[18]相比,侵蝕紅壤區(qū)馬尾松林0～20 cm土壤C、N、P質(zhì)量分?jǐn)?shù)顯著偏低。按照第2次全國土壤普查技術(shù)標(biāo)準(zhǔn)[19](0～20 cm土壤養(yǎng)分質(zhì)量分?jǐn)?shù)分為6級(jí),其中第1級(jí)為最高級(jí),第6級(jí)為最低級(jí)),土壤C的平均質(zhì)量分?jǐn)?shù),CK1和恢復(fù)2 a的馬尾松林土壤處于第6級(jí)(＜3.5 g/kg),恢復(fù)13～33 a的馬尾松林土壤處于第4級(jí)(5.8～11.6 g/kg),CK2土壤則處于第3級(jí)(11.6～17.4 g/kg);土壤N的平均質(zhì)量分?jǐn)?shù),CK1和恢復(fù)2 a的馬尾松林土壤處于第6級(jí)(＜0.5 g/ kg),恢復(fù)13～33 a的馬尾松林土壤處于第5級(jí)(0.5～0.75 g/kg),CK2土壤則處于第4級(jí)(0.75～1.0 g/kg);P的平均質(zhì)量分?jǐn)?shù),馬尾松林土壤均處于第6級(jí)(＜0.4 g/kg)。

植被恢復(fù)過程中,土壤C、N、P質(zhì)量分?jǐn)?shù)的變化速率并不相同,恢復(fù)2 a的馬尾松林土壤C、N、P質(zhì)量分?jǐn)?shù)的變化主要是因?yàn)樵谥卫磉^程中施用有機(jī)復(fù)混肥和追肥的緣故。隨著恢復(fù)年限的增加,前期施用的肥料,肥效逐漸降低,植被恢復(fù)對土壤C、N、P質(zhì)量分?jǐn)?shù)的影響效應(yīng)逐漸顯現(xiàn),由于土壤中C、N、P的來源和保持機(jī)制不同,其變化速率也有較大差異。土壤碳主要來自植物枯落物的歸還,因此植被的快速恢復(fù)重建生態(tài)系統(tǒng)的物質(zhì)循環(huán),可以顯著增加土壤有機(jī)碳的質(zhì)量分?jǐn)?shù)。本研究中,通過收割法調(diào)查2區(qū)芒萁枯落物量分別為0.21和0.11 t/hm2,恢復(fù)13 a的馬尾松林厚厚的芒萁枯死物在地表形成大量的輕組有機(jī)碳,因而恢復(fù)13 a的馬尾松林0～10 cm土壤C質(zhì)量分?jǐn)?shù)顯著高于恢復(fù)30 a的馬尾松林土壤C質(zhì)量分?jǐn)?shù)。土壤氮素主要來源于生物固氮作用和植物殘?bào)w的歸還。本研究中恢復(fù)30～33 a的0～10 cm土壤N質(zhì)量分?jǐn)?shù)顯著高于恢復(fù)2～13 a土壤N質(zhì)量分?jǐn)?shù),說明植被恢復(fù)過程中,0～10 cm土壤環(huán)境逐漸改善,土壤生態(tài)系統(tǒng)的N保持能力也逐漸增強(qiáng);但不同恢復(fù)年限10～20 cm土壤N質(zhì)量分?jǐn)?shù)差異不顯著。D.A.Wardle等[20]的長期觀測實(shí)驗(yàn)也發(fā)現(xiàn),隨土壤恢復(fù)年限增加,土壤N質(zhì)量分?jǐn)?shù)有所提高但是增加緩慢。本研究中土壤P質(zhì)量分?jǐn)?shù)(變化范圍為0.04～0.12 g/kg)顯著較低,這是南方亞熱帶土壤的特性[21],P的缺乏導(dǎo)致微生物生長活動(dòng)受到限制,影響土壤酶的分泌[22]及土壤N礦化,由此導(dǎo)致土壤中N質(zhì)量分?jǐn)?shù)增加緩慢。以上分析表明,盡管恢復(fù)30 a以上的馬尾松林土壤C、N、P質(zhì)量分?jǐn)?shù)比未治理的侵蝕紅壤已有顯著增加,但是土壤C、N質(zhì)量分?jǐn)?shù)仍顯著低于CK2,如恢復(fù)33 a的馬尾松林土壤C、N質(zhì)量分?jǐn)?shù)分別僅為CK2土壤C、N質(zhì)量分?jǐn)?shù)的59%～70%、36%～53%。這表明侵蝕恢復(fù)土壤仍很貧瘠,土壤碳和養(yǎng)分的恢復(fù)是一個(gè)長期的過程。

4.2不同恢復(fù)年限馬尾松林土壤C∶N、C∶P、N∶P化學(xué)計(jì)量比特征及養(yǎng)分限制

土壤C∶N是預(yù)測有機(jī)質(zhì)分解速率的有效指標(biāo),一般與其分解速率呈反比[23]。本研究未治理侵蝕地(CK1)0～10、10～20 cm土壤C∶N(均值分別為8.80、7.14)均顯著低于福建省0～20 cm紅壤C∶N (均值為14.8)[17],說明未治理侵蝕地(CK1)C∶N嚴(yán)重失衡;恢復(fù)13、30 a的馬尾松林0～10 cm土壤C∶N(均值分別為16.51、16.82)和CK2土壤的C∶N (均值為15.49)比值無顯著性差異,說明恢復(fù)13～30 a土壤C∶N逐漸趨向平衡?；謴?fù)2～33 a土壤C∶N低于微生物所需的最適底物組織C∶N(約為25)[23],說明恢復(fù)2～33 a時(shí),土壤有機(jī)質(zhì)分解較快,氮素在積累。S.F.Chapin等[24]也表示C∶N較低時(shí),氮超過微生物生長所需的部分就會(huì)釋放到凋落物和土壤中。土壤C∶P反映土壤磷有效性的高低。未治理侵蝕地(CK1)0～10、10～20 cm土壤的C∶P (均值分別為39.52、33.09)與福建省0～20 cm紅壤C∶P(均值為32.0)[17]接近,但恢復(fù)13～33 a馬尾松林0～10 cm土壤C∶P(均值分別為81.88、126.48、153.92)高于福建省紅壤C∶P。說明侵蝕紅壤植被恢復(fù)后,土壤C∶P嚴(yán)重失衡,土壤磷有效性低,但其土壤仍能較好的維持馬尾松林的生長,說明經(jīng)過長期的適應(yīng),馬尾松可能對低磷脅迫已形成較好的基本適應(yīng)對策。土壤N∶P可以作為衡量群落氮磷養(yǎng)分限制的1個(gè)指標(biāo),恢復(fù)2 a的馬尾松林0～10 cm土壤N∶P顯著高于CK1土壤N∶P,且恢復(fù)2～33 a土壤N∶P(均值分別為6.45、4.97、7.53、7.52)顯著高于福建省紅壤N∶P(均值為2.1)[17],次生林(CK2)0～10 cm土壤N∶P為11.5,高于中國土壤N∶P(均值為9.3)[25],而恢復(fù)2～33 a馬尾松林土壤N∶P仍遠(yuǎn)低于CK2土壤N∶P。說明侵蝕紅壤養(yǎng)分限制類型以P素為主,恢復(fù)侵蝕紅壤的馬尾松林土壤N∶P仍然失衡。

4.3馬尾松林土壤C、N、P與C∶N、C∶P、N∶P化學(xué)計(jì)量比的關(guān)系

侵蝕退化紅壤植被恢復(fù)過程中,土壤C∶N和C∶P與土壤C質(zhì)量分?jǐn)?shù)呈極顯著的正相關(guān)關(guān)系,說明土壤碳質(zhì)量分?jǐn)?shù)對養(yǎng)分具有良好的指示作用。土壤N∶P與N質(zhì)量分?jǐn)?shù)呈極顯著的正相關(guān)關(guān)系,與P質(zhì)量分?jǐn)?shù)無顯著相關(guān),而N、P質(zhì)量分?jǐn)?shù)之間表現(xiàn)為極顯著的正相關(guān)關(guān)系,說明侵蝕退化紅壤盡管P素缺乏;但在現(xiàn)階段的恢復(fù)過程中主要受N素控制,N素可能是主要的限制性養(yǎng)分,而P素則不敏感。綜上所述,侵蝕未治理裸地土壤各化學(xué)計(jì)量比嚴(yán)重失衡,土壤C、N、P質(zhì)量分?jǐn)?shù)難以得到補(bǔ)給和維持,侵蝕地植被恢復(fù)后,生態(tài)系統(tǒng)將趨于正向演替,土壤C∶N逐漸趨向平衡;但C∶P和N∶P仍然不平衡,下一階段植被恢復(fù)時(shí)可能受到土壤P的限制更為嚴(yán)重。

5 結(jié)論

未治理的嚴(yán)重侵蝕紅壤C、N、P的質(zhì)量分?jǐn)?shù)極低,化學(xué)計(jì)量比嚴(yán)重失衡。植被恢復(fù)顯著提高侵蝕紅壤的C、N、P的質(zhì)量分?jǐn)?shù),隨著恢復(fù)年限的增加,由于植被恢復(fù)不同階段的土壤C、N、P的質(zhì)量分?jǐn)?shù)的變化速率并不一致,土壤C∶N逐漸趨向平衡,但C∶P和N∶P仍很不平衡。按照全國第2次土壤普查技術(shù)標(biāo)準(zhǔn),侵蝕紅壤及其恢復(fù)的馬尾松林土壤均很貧瘠,治理恢復(fù)30 a以上的馬尾松林土壤C、N、P質(zhì)量分?jǐn)?shù)仍顯著低于次生林土壤,表明侵蝕紅壤的土壤肥力恢復(fù)是非常緩慢的,且恢復(fù)30 a后應(yīng)配施磷肥,避免侵蝕紅壤的恢復(fù)受到磷的限制。侵蝕紅壤植被恢復(fù)不同年限的土壤化學(xué)計(jì)量比與土壤C和N的質(zhì)量分?jǐn)?shù)顯著相關(guān),與P的質(zhì)量分?jǐn)?shù)相關(guān)性不顯著,暗示現(xiàn)階段侵蝕退化紅壤植被恢復(fù)可能對N素的響應(yīng)比對P素的響應(yīng)更為敏感。

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Ecological stoichiometry characteristics of eroded red soil in different restoration years

Zhang Qiufang1,2,Chen Naishou1,2,Chen Tan1,2,Lyu Maokui1,2,Yang Yusheng1,3,Xie Jinsheng1,3

(1.State Key Laboratory of Subtropical Mountain Ecology(Funded by Ministry of Science and Technology and Fujian Province), Fujian Normal University,350007,Fuzhou,China;2.College of Geographical Science,Fujian Normal University,350007,Fuzhou,China; 3.Institute of Geography,Fujian Normal University,350007,Fuzhou,China)

[Background]Large areas of degraded lands have been restored in red soil regions of south China since 1980s,which provides tremendous ecological and economic services such as soil and water conservation,carbon sequestration and environment protection.Some problems such as soil degradation, soil and water loss and tree disease decline,however,also appeared after several decades of ecological restoration due to lack of knowledge about soil characteristics,which seriously threatens the stability and sustainability of plantation.The contents of carbon,nitrogen,and phosphorous are important indexes of forestmanagement,which respond positively to the environmental conditions.In recent years,the ecological stoichiometry has received considerable attentions.However,few studies have been reported about the patterns of soil stoichiometry across ecological restoration.[M ethods]We took Pinus. massoniana woodlands as research objects,and determined the content variations of total organic carbon(C),total nitrogen(N),and total phosphorous(P)in soil,as well as ecological stoichiometric ratios across different ecological restoration years at 6 sites.Six P.massoniana woodlands were the ones restored by 0 year(CK1),2 years,13 years,30 years,33 years,and secondary forest(CK2), respectively.Those study sites were expected to be distinguished at the level of ecological restoration years along the typical eroded red soil region in Hetian town,Changting County,Fujian Province. [Results]1)The contents of C and N in soil increased in the restoring process of degraded red soil. However,the P content was not considerable changed.The soil C,N and P contents in the forest of restored 2-33 yearswere still significantly lower than those in CK2.2)The ratios of C∶N,C∶P and N∶P tended to increase with the restored years increasing,especially soil C∶N ratio of restored 2-33 yearswas approaching to those in CK2.3)C content and C∶N,C content and C∶P,N and N∶P all were in positive correlation,but P contenthad no significant correlation with N∶P.[Conclusions]Soil C,N and P contentswere out of balance in the non-restored eroded red soil(CK1).Despite some areas have been restored for 30 or 33 years,the nutrient contents still were lower than those in secondary forest(CK2). In other words,the typical eroded red soil restoration is a long-term process.Moreover,soil stoichiometry ratios weremainly restricted by soil C and N contents in the restoring process of degraded red soil.It suggests that a vegetation recovery ismore sensitive to N than to P at this typical eroded red soil region. Thus,this study will help to reveal the nutrient cycling of P.massoniana woodlands by combing with stoichiometric characteristics of soil C,N,and P comprehensively and systematically.Therefore,it is very important to guide the ecological restoration of eroded red soil,and further improving the productivity of forest system should be carried out.

eroded red soil;ecological restoration;Pinusmassoniana;stoichiometry

S154.1;X171.4

A

1672-3007(2016)02-0059-08

10.16843/j.sswc.2016.02.008

2015-05-25

2016-02-08

項(xiàng)目名稱:國家科技部973課題“亞熱帶紅壤侵蝕區(qū)森林恢復(fù)與保護(hù)的碳匯功能及潛力”(2012CB722203);國家自然科學(xué)基金“芒萁對退化紅壤碳積累的貢獻(xiàn)及關(guān)鍵影響機(jī)制”(31370465)

張秋芳(1991—),女,碩士研究生。主要研究方向:森林生態(tài)。E-mail:qiufangzh@foxmail.com

簡介:謝錦升(1972—),男,博士,教授。主要研究方向:碳循環(huán)及恢復(fù)生態(tài)。E-mail:jshxie@163.com