水曲柳和兴安落叶松人工林细根分解研究

doi:10.3773/j.issn.1005-264x.2008.06.003

摘要/Abstract

摘要：

细根分解是陆地生态系统C和养分循环的重要环节。以往的细根分解研究以埋袋法的应用为主。然而, 由于埋袋法对分解材料的干扰以及对分解环境的改变使其很难揭示原位环境下根系的自然分解过程。该研究应用微根管(Minirhizotron)技术连续3年对水曲柳(Fraxinus mandshurica)和兴安落叶松(Larix gmelinii)细根的分解过程进行原位监测, 运用Kaplan-Meier方法估算细根分解的保存率及分解期中位值(即50%细根完全分解的时间, Median root decomposition time), 做分解曲线, 用对数秩检验(Log-rank test)方法分析不同树种、直径、根序及土层对细根保存率的影响。结果表明, 伴随时间延长, 细根的保存率逐渐下降, 兴安落叶松细根保存率的下降显著快于水曲柳(p<0.001), 两树种分解期中位值分别为(82±7) d 和(317±28) d; 不同直径等级(≤0.3、0.3~0.6、>0.6 mm)细根的分解速率不同, 两树种最长分解期中位值均出现在最细直径(≤0.3 mm)根中; 高级根分解速率显著低于一级根(p<0.05); 土壤上层分解速度快, 随着土壤深度增加细根分解速率减小。微根管技术为了解细根自然分解过程提供了有效途径。

关键词: 水曲柳, 兴安落叶松, 细根分解, 微根管

Abstract:

Aims Fine root decomposition is a major pathway of carbon and nutrient cycling in terrestrial ecosystems. Litterbag studies change the environmental conditions of root decay, so we employed a minirhizotron technique. Our objectives were to: 1) compare fine-root decomposition time and rate between ash (Fraxinus mandshurica) and larch (Larix gmelinii) in the same site, 2) analyze the effect of root diameter and root order on fine root decomposition and 3) investigate patterns of fine root decomposition in different soil depths.

Methods In October 2003, we established three 20 m × 30 m plots in each plantation, and randomly installed six minirhizotron tubes. From April 2004 to October 2006, video images were collected at approximately two-week intervals during the growing season. The interval from date of root death to disappearance was defined as decomposition time. Video images were digitized via RooTracker software (NC, USA). Kaplan-Meier method in survival analysis was used to generate cumulative remaining rate and median root decomposition time (MRDT), and factors of tree species, diameter, root order and soil depth were compared by logrank test.

Important findings Cumulative remaining rate of fine-roots in both species decreased gradually with time, with the decrease significantly faster for larch than ash (p<0.001).MRDT of larch was (82±7) d compared with (317±28) d for ash. TheMRDT of both species differed in three diameter classes (≤0.3, 0.3-0.6 and >0.6 mm). The finest roots (≤0.3 mm) of both ash and larch decayed slower than the other two diameter classes; however, only theMRDT of ash decreased systematically with increasing root diameter. With increasing root order, the cumulative remaining rate of both species increased significantly (p<0.05), resulting in a delay time of 82 d and 58 d ofMRDT for higher order compared with first order in larch and ash roots, respectively. The fine-root cumulative remaining rate of both species showed similar pattern among soil depths, which at 0-15 cm depth was significantly less than 15-30 and 30-45 cm (p<0.01). This study suggested that fine-root decomposition is a species-specific process, mutually controlled by internal factors (e.g., diameter) and external factors (i.e., soil depth). Decay of fine roots is faster than previous reported.

Key words: Fraxinus mandshurica, Larix gmelinii, fine-root decomposition, minirhizotron

宋森, 谷加存, 全先奎, 郭大立, 王政权. 水曲柳和兴安落叶松人工林细根分解研究. 植物生态学报, 2008, 32(6): 1227-1237. DOI: 10.3773/j.issn.1005-264x.2008.06.003

SONG Sen, GU Jia-Cun, QUAN Xian-Kui, GUO Da-Li, WANG Zheng-Quan. FINE-ROOT DECOMPOSITION OF FRAXINUS MANDSHURICA AND LARIX GMELINII PLANTATIONS. Chinese Journal of Plant Ecology, 2008, 32(6): 1227-1237. DOI: 10.3773/j.issn.1005-264x.2008.06.003

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链接本文: https://www.plant-ecology.com/CN/10.3773/j.issn.1005-264x.2008.06.003

https://www.plant-ecology.com/CN/Y2008/V32/I6/1227

图/表 6

图5 落叶松细根动态影像

Fig. 5 Minirhizotron images illustrating fine root dynamics for Larix gmelinii

图1 兴安落叶松和水曲柳细根保存率比较

Fig. 1 Comparison of fine root remaining rate for Larix gmelinii and Fraxinus mandshurica

图2 兴安落叶松和水曲柳不同直径等级细根保存率比较

Fig. 2 Comparison of fine root remaining rate of different diameter classes for Larix gmelinii and Fraxinus mandshurica

表1 兴安落叶松和水曲柳总体细根及不同直径、不同根序、不同土层细根的中位值分解期和平均分解期(p<0.05)

Table 1 Median and mean decomposition time for different diameter, root order and soil depth of Larix gmelinii and Fraxinus mandshurica fine roots (median, mean ± SE) (p<0.05)

	兴安落叶松 Larix gmelinii		水曲柳 Fraxinus mandshurica
	中位值分解期 Median decomposition time (d)	平均分解期 Mean decomposition time (d)	中位值分解期 Median decomposition time (d)	平均分解期 Mean decomposition time (d)
总体 Total	82±7^b	199±17	317±28^a	353±20
直径 Diameter (mm)
≤0.3	246±138^a	205±32	323±38^a	398±39
0.3~0.6	69±5^a	175±19	309±68^a	339±26
>0.6	85±53^a	273±53	273±104^a	312±47
根序 Root order
一级 First order	62±5^b	153±17	302±26^b	328±23
高级 High order	144±33^a	219±36	360±58^a	415±61
土层 Soil depth (cm)
0~15	64±2^c	128±16	316±65^c	341±25
15~30	93± 21^b	222±29	373±61^b	374±39
30~45	246±51^a	306±46	396±13^a	421±55

图3 兴安落叶松和水曲柳不同根序细根保存率比较

Fig. 3 Comparison of fine root remaining rate of different root order for Larix gmelinii and Fraxinus mandshurica

图4 兴安落叶松和水曲柳不同土层细根保存率比较

Fig. 4 Comparison of fine root remaining rate of different soil layers for Larix gmelinii and Fraxinus mandshurica

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