内蒙古东部天然白桦林的凋落物性质和储量及其随温度和降水梯度的变化格局

doi:10.3773/j.issn.1005-264x.2010.09.001

摘要/Abstract

摘要：

作为碳素和养分循环的重要组分, 地表凋落物如何响应全球气候变化日益受到重视。中国北方半干旱地区森林草原过渡带斑块状分布的森林对气候变化引起的水热变化的响应较为敏感, 但是对这些森林地表处于不同分解阶段的凋落物的化学性质和储量的格局及其如何响应温度、降水变化的报道较少。该研究分析了内蒙古东部地区处于年平均气温和年降水量梯度上的12个天然白桦(Betula platyphylla)林不同凋落物层次(最上层的初步分解层L1, 中间的半分解层L2, 最下层的腐殖质层L3)的化学性质及现存量后发现: 1)随着分解的进行(即从L1到L3层), 氮、磷浓度显著增加, 可提取物浓度基本不变, 酸溶性组分(acid soluble fraction, AS)浓度下降, 酸不溶性组分(acid insoluble fraction, AIF)浓度增加。2)各元素现存量均在L3层最高, 表明凋落物分解缓慢, 养分积累。3)年平均气温和年降水量对凋落物有机组分(AS组分和AIF组分)的性质无显著影响, 但L3层元素储量随年平均气温升高而增加, 可能由于年平均气温较高的地点森林生产力更高, 从而导致叶凋落物量增加, 但由于受水分限制(尤其是在夏天), 这些地点的凋落物分解速率不变或更低, 使凋落物积累更为明显。上述结果表明: 腐殖质层是这些白桦林的一个重要的碳及养分库, 未来在降水没有明显变化的情况下, 这一区域的升温可能会增加白桦林地表凋落物储量。

关键词: 白桦, 分解, 凋落物, 降水, 温度

Abstract:

Aims Forest litter is both a large source of CO₂ released from terrestrial ecosystems to the atmosphere and a critical sink of carbon and nutrients for plant growth. Studying dynamics of forest litter and its response to temperature and precipitation changes can improve our understanding of forest carbon and nutrient cycles and their interactions with projected climate change. Our objective was to examine the stocks and chemical quality of forest litter in natural birch (Betula platyphylla) forests that vary in both annual mean temperature (AMT) and annual mean precipitation (AMP).

Methods During July and August 2008, we measured the standing stocks and concentrations of carbon, nitrogen and phosphorus and organic fractions (extractives, acid soluble fraction (AS) and acid insoluble fraction (AIF)) of three litter layers (L1: slightly decomposed layer, L2: half-decomposed layer and L3: humus layer) in the forest floor of 12 birch forests in Inner Mongolia, China.

Important findings Along the decomposition gradient (i.e., from L1 to L3), nitrogen and phosphorus concentrations increased, AS concentration decreased, AIF concentration increased but extractives did not show significant change. Temperature and precipitation did not have significant effects on carbon fractions but at sites where AMT was higher, carbon stocks in L3 layer were higher, probably because of greater accumulation at higher-temperature sites as a result of higher litter production but similar decomposition rate compared to lower-temperature sites. These findings indicate that the litter layer (particularly the L3 layer) is an important carbon and nutrient pool at the ecosystem scale and future increases in temperature without concurrent increases in precipitation may enhance litter accumulation in these natural birch forests.

Key words: Betula platyphylla, decomposition, litter, precipitation, temperature

陈莎莎, 刘鸿雁, 郭大立. 内蒙古东部天然白桦林的凋落物性质和储量及其随温度和降水梯度的变化格局. 植物生态学报, 2010, 34(9): 1007-1015. DOI: 10.3773/j.issn.1005-264x.2010.09.001

CHEN Sha-Sha, LIU Hong-Yan, GUO Da-Li. Litter stocks and chemical quality of natural birch forests along temperature and precipitation gradients in eastern Inner Mongolia, China. Chinese Journal of Plant Ecology, 2010, 34(9): 1007-1015. DOI: 10.3773/j.issn.1005-264x.2010.09.001

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链接本文: https://www.plant-ecology.com/CN/10.3773/j.issn.1005-264x.2010.09.001

https://www.plant-ecology.com/CN/Y2010/V34/I9/1007

图/表 7

表1 内蒙古东部12个天然白桦林样点描述

Table 1 Site description of 12 sampling sites in Eastern Inner Mongolia

地点 Site	缩写 Abbreviation	经度 Longitude (°) (E)	纬度 Latitude (°) (N)	海拔 Altitude (m)	坡度 Slope (°)	温度梯度 Temperature gradient	降水梯度 Precipitation gradient	胸径 DBH (cm)	胸高断面积 Basal area (m²·hm^-2)	凋落物现存量 Litter stock (g·m^-2)
罕山 Hanshan	HS	118.71	44.19	1389.0	26	T4	Pre3	14.8	59.7	3 614.2
太本 Taiben	TB	118.64	44.57	1330.0	23	T4	Pre2	23.0	48.1	3 686.9
高力罕 Gaolihan	GLH	118.35	44.85	1214.0	17	T4	Pre1	18.2	10.6	3 194.5
海日罕 Hairihan	HRH	120.33	45.99	884.8	15	T3	Pre3	7.2	12.7	1 694.8
阿尔昆 A’erkun	AEK	119.82	45.33	962.8	28	T3	Pre2	7.6	20.0	614.5
宝日格斯台 Baorigesitai	BRG	118.92	44.99	1 176.0	16	T3	Pre1	15.1	58.4	3 881.0
阿尔山 A’ershan	AES	119.98	47.16	1 125.0	8	T2	Pre3	9.5	35.3	3 183.7
杜拉尔 Dula’er	DLE	119.69	47.34	940.0	13	T2	Pre2	10.8	42.8	1 520.3
罕达盖 Handagai	HDG	119.47	47.45	885.5	33	T2	Pre1	9.6	36.9	2 285.1
姑子庙 Guzimiao	GZM	120.69	50.40	662.7	14	T1	Pre3	12.3	64.6	2 760.8
小乌尔根 Xiaowu’ergen	XWEG	120.48	50.38	633.5	26	T1	Pre2	13.7	47.5	2 756.4
额尔古纳 E’erguna	EEGN	120.23	50.35	666.0	15	T1	Pre1	9.4	40.2	2 370.1

图1 内蒙古12个样地凋落物各个层次在不同年降水量(Pre)和年平均气温(T)梯度下的平均碳(A-C)、氮(D-F)、磷(G-I)的浓度。 T1-T4分别表示-3.0、-2.4、2.3和3.2 ℃ 4个温度梯度, Pre1-Pre3分别表示373、394和415 mm 3个降水梯度。不同小写字母表示在某个降水条件下同一层次不同温度间元素浓度的差异显著, p < 0.05。小于3个数据的没有标注字母。

Fig. 1 Mean C (A-C), N (D-F) and P (G-I) concentrations of different litter layers along precipitation and temperature gradients. T1-T4 represent four annual average air temperature gradients of -3.0, -2.4, 2.3 and 3.2 ℃, respectively. Pre1-Pre3 represent three annual average precipitation gradients of 373, 394 and 415 mm, respectively. Different lower-case letters represent significant differences (p < 0.05) in elemental concentrations of the same layer in a certain precipitation gradient among four temperature gradients. Item that has less than three values has no letter labelled.

表2 凋落物层次、温度、降水对凋落物平均碳、氮、磷浓度, 储量以及有机组分含量的影响的方差分析结果

Table 2 ANOVA results of the effects of litter layer, temperature and precipitation on the mean concentrations and stocks of C, N, and P, and concentrations of chemical fractions

	L	L × T	L × Pre	L × T × Pre	T	Pre	T × Pre
碳浓度 C concentration	<0.001	0.327	0.746	0.885	0.000	0.136	0.037
氮浓度 N concentration	<0.001	0.006	0.929	0.006	0.018	0.065	0.021
磷浓度 P concentration	<0.001	0.004	0.397	0.002	<0.001	0.013	<0.001
可提取物浓度 Extractives concentration	0.010	0.242	0.623	0.105	0.412	0.772	0.021
酸溶性组分浓度 Acid soluble fraction concentration	<0.001	0.029	0.054	0.028	0.406	0.122	0.009
酸不溶性组分浓度 Acid insoluble fraction concentration	0.005	0.091	0.246	0.037	0.239	0.212	0.021
碳储量 C stock	<0.001	0.018	0.173	0.017	0.018	0.446	0.003
氮储量 N stock	<0.001	0.003	0.094	0.002	0.001	0.446	0.001
磷储量 P stock	<0.001	0.001	0.012	<0.001	<0.001	0.225	<0.001

表3 温度、降水对叶片和凋落物各个层次碳、氮、磷浓度和储量以及有机组分含量的影响的方差分析结果

Table 3 ANOVA results of the effects of temperature and precipitation on the concentrations and stocks of C, N, and P, and the concentrations of organic fractions of leaf and litter layers

	L1			L2			L3
	T	Pre	T × Pre	T	Pre	T × Pre	T	Pre	T × Pre
碳浓度 C concentration	> 0.05	> 0.05	> 0.05	0.001	> 0.05	0.004	0.015	> 0.05	> 0.05
氮浓度 N concentration	0.014	0.017	0.002	< 0.001	0.022	0.004	> 0.05	0.021	> 0.05
磷浓度 P concentration	< 0.001	0.031	< 0.001	< 0.001	0.004	0.010	> 0.05	0.038	< 0.001
可提取物浓度 Extractives concentration	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05	0.002	> 0.05	> 0.05	> 0.05
酸溶性组分浓度 Acid soluble fraction concentration	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05	> 0.05
酸不溶性组分浓度 Acid insoluble fraction concentration	> 0.05	> 0.05	> 0.05	> 0.05	0.045	0.002	> 0.05	> 0.05	> 0.05
碳储量 C stock	> 0.05	0.035	> 0.05	> 0.05	0.037	> 0.05	0.003	0.024	0.002
氮储量 N stock	0.044	> 0.05	0.011	> 0.05	0.026	> 0.05	< 0.001	0.009	< 0.001
磷储量 P stock	0.025	> 0.05	0.020	> 0.05	0.019	> 0.05	< 0.001	0.002	0.001

图2 不同层次凋落物可提取物(A)、酸溶性组分(B)、酸不溶性组分(C)浓度。不同小写字母表示某个有机组分在3个凋落物层次间的差异显著, p < 0.05。L1- L3同表3。

Fig. 2 Average concentrations of extractives (A), acid soluble fraction (B), and acid insoluble fraction (C) of different litter layers. Different lower-case letters represent significant differences (p < 0.05) in the concentrations of organic fractions among three litter layers. L1- L3 see Table 3.

图3 12个样地凋落物各个层次在不同降水梯度(Pre1-Pre3)和温度梯度(T1-T4)下的平均可提取物(A-C)、酸溶性组分(D-F)、酸不溶性组分(G-I)的浓度。不同小写字母表示在某个降水条件下同一层次不同温度间有机组分浓度的差异显著, p < 0.05。小于3个数据的没有标注字母。T1-T4, Prel-Pre3, 同图1。

Fig. 3 Mean concentrations of extractives (A-C), acid soluble fraction (D-F), and acid insoluble fraction (G-I) of different litter layers along precipitation (Pre1-Pre3) and temperature gradients (T1-T4). Different lower-case letters represent significant differences (p < 0.05) in concentrations of organic fractions of the same layer in a certain precipitation gradient among four temperature gradients. Item that has less than three values has no letter labelled. T1-T4, Prel-Pre3, see Fig. 1.

图4 内蒙古12个样地凋落物各个层次在不同降水梯度(Pre1-Pre3)和温度梯度(T1-T4)下的平均碳(A-C)、氮(D-F)、磷(G-I)储量。不同小写字母表示在某个降水条件下同一层次不同温度间元素储量间的差异显著, p < 0.05。小于3个数据的没有标注字母。T1-T4, Prel-Pre3, 同图1。

Fig. 4 Mean stocks of C (A-C), N (D-F) and P (G-I) of different litter layers along precipitation (Pre1-Pre3) and temperature gradients (T1-T4). Different lower-case letters represent significant differences (p < 0.05) in the stocks of C, N, and P of the same layer in a certain precipitation gradient among four temperature gradients. Item that has less than three values has no letter labelled. T1-T4, Prel-Pre3, see Fig. 1.

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