曾 冀，雷淵才，賈宏炎，蔡道雄，唐繼新

(1.中國林業(yè)科學(xué)研究院熱帶林業(yè)實(shí)驗(yàn)中心，廣西 憑祥 532600; 2. 中國林業(yè)科學(xué)研究院資源信息研究所，北京 100091)

桂西南馬尾松人工林生長對(duì)不同強(qiáng)度采伐的動(dòng)態(tài)響應(yīng)*

曾 冀1,2，雷淵才2**，賈宏炎1，蔡道雄1，唐繼新1

(1.中國林業(yè)科學(xué)研究院熱帶林業(yè)實(shí)驗(yàn)中心，廣西 憑祥 532600; 2. 中國林業(yè)科學(xué)研究院資源信息研究所，北京 100091)

馬尾松；強(qiáng)度采伐；密度效應(yīng)；生長動(dòng)態(tài)

馬尾松(PinusmassonianaLamb.) 是我國南方亞熱帶地區(qū)分布最廣、資源最多的松類樹種，不僅具有很高的經(jīng)濟(jì)價(jià)值，而且在森林生態(tài)系統(tǒng)恢復(fù)和重建中發(fā)揮著重要作用[1]。桂西南地區(qū)熱量豐富、雨量充沛且雨熱同季，是馬尾松高產(chǎn)區(qū)之一；然而，由于大面積成片馬尾松純林經(jīng)營，出現(xiàn)蟲害頻發(fā)、生態(tài)功能下降等問題[2]。為解決馬尾松蟲害問題，中國林業(yè)科學(xué)研究院熱帶林業(yè)實(shí)驗(yàn)中心(以下簡稱熱林中心) 自2005年以來，陸續(xù)開展了馬尾松人工林近自然化改造的探索,方法是選擇適宜的采伐強(qiáng)度，在林下套種鄉(xiāng)土闊葉樹進(jìn)行馬尾松人工純林近自然化改造，促進(jìn)其向馬尾松-闊葉異齡林的轉(zhuǎn)變，并加快馬尾松大徑材培育速度。本研究于2007年，對(duì)熱林中心14年生馬尾松人工林開始進(jìn)行近自然化改造的不同強(qiáng)度采伐試驗(yàn)，定期開展生長觀測，以期揭示不同強(qiáng)度采伐下馬尾松林分的生長動(dòng)態(tài)，為完善馬尾松人工林近自然經(jīng)營提供參考。

早在19世紀(jì)，瑞士和斯洛文尼亞即開展近自然森林經(jīng)營研究，Schütz[3]研究了近自然化改造100年后的歐洲橡樹林，發(fā)現(xiàn)近自然森林經(jīng)營能很好地解決采伐和天然更新等經(jīng)營問題。Ward[4]對(duì)北美紅櫟(QuercusrubraL.) 及Miller[5]對(duì)北美紅櫟 、山櫟(QuercusprinusL.) 、美國黑櫻桃(PrunusserotinaEhrh.)和黃楊木(LiriodendrontulipiferaL.)的研究均表明，采伐能促進(jìn)幼齡林的胸徑生長。Smith等[6]對(duì)北美紅櫟及Stringer等[7]對(duì)白櫟(QuercusfabriHance)的研究發(fā)現(xiàn)，強(qiáng)度采伐亦能促進(jìn)成熟林的胸徑生長。Trimble[8]對(duì)黃楊木和美國黑櫻桃及Lamson等[9]對(duì)加拿大糖槭(AcernegundoLinn.)的一些研究認(rèn)為,采伐會(huì)減緩樹高生長；Smith等[10]的研究則認(rèn)為,采伐對(duì)美國黑櫻桃、加拿大糖槭的樹高生長基本無影響，但對(duì)黃楊木的樹高生長具促進(jìn)作用。相對(duì)于常規(guī)間伐，近自然經(jīng)營中的采伐強(qiáng)度更大，主要針對(duì)林分中的目標(biāo)樹進(jìn)行單株管理，使目標(biāo)樹在較短的時(shí)間內(nèi)達(dá)到目標(biāo)胸徑[11]。從國內(nèi)有關(guān)近自然經(jīng)營采伐的研究報(bào)道可看出，大部分是關(guān)于采伐后的林下物種多樣性[12]、森林更新[13]和目標(biāo)樹生長[14]等研究，而關(guān)于林木生長對(duì)采伐的動(dòng)態(tài)響應(yīng)研究較少，僅李婷婷等[15]研究了杉木人工林近自然化改造后的林分生長，比較了47%和61%兩個(gè)強(qiáng)度采伐后4年內(nèi)林分蓄積生長量和單木生長量等動(dòng)態(tài)變化。盡管目前已有一些關(guān)于馬尾松、杉木間伐方面的研究[16-18]，而對(duì)不同強(qiáng)度采伐后的馬尾松生長動(dòng)態(tài)鮮有報(bào)道。為此，本文利用馬尾松近自然改造試驗(yàn)林，以系統(tǒng)研究馬尾松生長指標(biāo)與采伐強(qiáng)度間的相關(guān)性，為馬尾松人工林近自然化改造工作提供依據(jù)和指導(dǎo)。

1 試驗(yàn)地概況

1993年，在熱林中心伏波實(shí)驗(yàn)場用種源為寧明桐棉的1年生裸根苗營造馬尾松人工純林，株行距為2.0 m×2.5 m，初植密度為2 000株·hm-2,于1999年和2003年分別進(jìn)行了強(qiáng)度約20%的透光伐和強(qiáng)度約30%的撫育性間伐。

2 研究方法

2.1 試驗(yàn)設(shè)計(jì)

表1 樣地概況

注：Ⅰ、Ⅱ、Ⅲ和Ⅳ表示處理，其采伐強(qiáng)度分別為80%、73%、66%和59%；下標(biāo)為區(qū)組編號(hào)。

Notes: Ⅰ, Ⅱ, Ⅲ and Ⅳ refer to thinning treatments, and their intensities are 80%, 73%, 66% and 59%, respectively; and their subscripts are codes of blocks in the experiment.

2.2 生長觀測

采伐作業(yè)前，在馬尾松純林內(nèi)設(shè)置3塊400 m2的圓形樣地進(jìn)行本底調(diào)查，調(diào)查樣地內(nèi)所有馬尾松植株的胸徑、樹高、枝下高和冠幅。應(yīng)用圍尺進(jìn)行每木檢尺，采用皮尺分東、西、南、北4個(gè)方向測定冠幅，VERTEX超聲波測高器測量樹高和枝下高。林分平均保留密度為1 100株·hm-2，平均胸徑18.26 cm，平均樹高11.64 m，平均蓄積量150.25 m3·hm-2。采伐后，在每個(gè)小區(qū)中心位置附近選取一個(gè)圓心點(diǎn)布設(shè)半徑為11.3 m、面積400 m2的圓形樣地，分別于2008、2010、2012、2014年底和2016年8月對(duì)所有保留木進(jìn)行生長觀測。

2.3 數(shù)據(jù)處理

冠面積為東西、南北2個(gè)方向冠幅的乘積。

單株材積(V):V=g×f×h

式中：h為全樹高(m)；g為胸高斷面積(m2)；f為平均實(shí)驗(yàn)形數(shù)，馬尾松取0.39[19]。

采用單因素方差分析和Duncan多重比較檢驗(yàn)不同采伐強(qiáng)度下馬尾松林分的胸徑、樹高、單株材積和蓄積年均增長量及枝下高、冠面積年均變化量，應(yīng)用SPSS16.0 軟件進(jìn)行數(shù)據(jù)統(tǒng)計(jì)分析。由于套種的植株尚未進(jìn)入主林層，對(duì)馬尾松生長的影響較小，故本研究在分析生長動(dòng)態(tài)時(shí)未予考慮。

3 結(jié)果與分析

3.1 胸徑生長動(dòng)態(tài)

表2 采伐后第1年和第9年馬尾松林分的生長表現(xiàn)

注：表中字母為Duncan多重比較結(jié)果，處理間具相同字母表示差異不顯著(P≥0.05), 不同字母表示差異顯著(P<0.05)。

Note: Values followed by the same letters in a column are not significantly different among treatments at 0.05 level according to Duncan’s multiple range tests.

圖1 不同采伐強(qiáng)度馬尾松人工林胸徑年均增長量(大寫字母表示同一采伐強(qiáng)度處理年際間差異；小寫字母表示同一年份采伐強(qiáng)度處理間的差異。具相同字母表示差異不顯著(P≥0.05)；不同字母表示差異顯著(P<0.05)，下同。)
Fig.1 Mean annual growth rate of diameter at breast height(DBH) in Pinus massoniana plantations after thinning with different intensities (Colum values with the same lowercase and capital letters are not significantly different among years after thinning with each intensity and among thinning treatments in each year according to Duncan’s multiple range tests at the 5% level. The same below.)

3.2 樹高生長動(dòng)態(tài)

圖2 不同采伐強(qiáng)度馬尾松人工林樹高年均增長量
Fig. 2 Mean annual growth rate of height in Pinus massoniana plantations after thinning with different intensities

3.3 枝下高動(dòng)態(tài)變化

圖3 不同采伐強(qiáng)度馬尾松人工林枝下高年均增長量
Fig.3 Mean annual increase of crown base height (CBH) in Pinus massoniana plantations after thinning with different intensities

3.4 冠面積動(dòng)態(tài)變化

圖4 不同采伐強(qiáng)度馬尾松人工林冠面積年均增長量
Fig.4 Mean annual growth rate of crown area (CA) in Pinus massoniana plantations after thinning with different intensities

3.5 單株材積生長動(dòng)態(tài)

圖5 不同采伐強(qiáng)度馬尾松人工林單株材積年均增長量
Fig.5 Mean annual growth rate of individual tree volume (ITV) in Pinus massoniana plantations after thinning with different intensities

3.6 馬尾松林分蓄積動(dòng)態(tài)變化

圖6 不同采伐強(qiáng)度馬尾松人工林蓄積年均增長量
Fig.6 Mean annual growth rate of stand volume (SV) in Pinus massoniana plantations after thinning with different intensities

4 討論

林下套種闊葉樹對(duì)保留木生長存在一定的影響，但本研究未考慮其對(duì)上層林木的影響；然而，隨著時(shí)間的推移可能逐漸出現(xiàn)套種林木與馬尾松的水肥競爭。另一方面，闊葉樹的凋落物分解快，可以加速林地的養(yǎng)分循環(huán)，從而對(duì)林下物種多樣性、土壤等亦會(huì)產(chǎn)生積極影響。不同強(qiáng)度采伐后，林分的恢復(fù)是一個(gè)長期的過程，采伐強(qiáng)度越大，則影響的持續(xù)時(shí)間越長[31]。總而言之，本研究只是采伐后馬尾松生長動(dòng)態(tài)研究的階段性總結(jié)，未來闊葉樹逐漸進(jìn)入主林層，馬尾松的生長動(dòng)態(tài)必然會(huì)受影響；林下植被的變化亦會(huì)影響地力，進(jìn)而影響林分生產(chǎn)力[32-34]，有待長期觀測研究。

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(責(zé)任編輯：徐玉秀)

Dynamic Growth Response ofPinusMassonianaPlantation on Intensive Thinning in Southwestern Guangxi, China

ZENGJi1,2,LEIYuan-cai2,JIAHong-yan1,CAIDao-xiong1,TANGJi-xin1

(1. Tropical Forestry Research Center , Chinese Academy of Forestry, Pingxiang 532600, Guangxi，Chian; 2. Research Institute of Forest Resources Information Techniques, Chinese Academy of Forestry, Beijing 100091，Chian)

[Objective]Growth dynamics of Pinus massoniana were studied under intensive thinning so as to screen out suitable thinning intensity and provide technical support for close-to-nature management of Masson pine plantations. [Method] A thinning trial was conducted in a 14-year-old Masson pine plantation with stand density of 1 100 trees per hectare in October, 2007. Four thinning treatments including 225, 300, 375 and 450 trees left per hectare and the control without thinning were arranged. Since 2008, growth performance such as diameter at breast height (DBH), height, height of crown base and crown area were measured every two years, and wood volumes were calculated at the single tree and stand level. These data were analyzed through one-way variance analysis and Duncan multiple range tests to reveal dynamical responses of these index to all sorts of thinning intensities. [Result] Stand growth performance were significantly influenced by thinning intensity, mean annual increments of DBH, single tree volume, crown area decreases with increase of stand density of thinning treatments, but they were all significantly higher than those of the control (P<0.05). The crown area increments of Masson pine were the highest during year 1 to 3 after thinning, while increments of DBH were the highest during year 3 to 5. No obvious relationship was observed between tree height growth rate and thinning density. Increases of crown base height and stand volume were significantly affected by stand density, and they increased with increase of stand density, while the differences of stand volume decreased with increase of forest age. [Conclusion] In the present study, Masson pine’s response of crown growth to intensive thinning was the most sensitive and rapid. The crown area increased sharply at first, then resulted in rapid growth of DBH, while tree height and crown base height increased a bit stably. Thinning with four intensities all remarkably influenced the growth of single tree volume, but only thinning with 225 trees left per hectare had significant effect on increment of stand volume. Taking mean annual increments of the single tree volume and stand volume, thinning intensity with 300 trees left per hectare was recommended for close-to-nature management of 15-year-old Masson pine plantations in southwestern Guangxi.

Pinusmassoniana; intensive thinning; density effect; growth dynamics

2016-09-23 基金項(xiàng)目： 全國森林經(jīng)營基礎(chǔ)研究項(xiàng)目(169201531)及中國林業(yè)科學(xué)研究院熱帶林業(yè)實(shí)驗(yàn)中心主任基金(RL-2012-02) 作者簡介： 曾 冀(1981—)，男，四川自貢人，在讀博士生，工程師，主要從事森林培育與經(jīng)營研究. * 致謝：承蒙中國林業(yè)科學(xué)研究院熱帶林業(yè)研究所曾杰研究員審閱修改論文，特致謝忱！ ** 通訊作者.

10.13275/j.cnki.lykxyj.2017.02.021

S791.248

A

1001-1498(2017)02-0335-07