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1.
Biomass and production of fine roots in Japanese forests   总被引：1，自引：0，他引：1  
To better understand the control of fine-root dynamics in Japanese forests, we reviewed studies conducted in Japan on fine-root biomass and production. Most of the data on fine-root biomass were obtained for conifer plantations in limited regions; the average fine-root biomass of dominant trees ranged from ∼50 g m−2 for Pinus species (n = 3) to ∼600 g m−2 for Cryptomeria japonica (n = 4) and Chamaecyparis obtusa (n = 3). These values are comparable with or less than those reported for other temperate forests mainly in North America or Europe. Information on fine-root production in Japanese forests remains limited. Fine-root production accounted for ∼30% of the net primary productivity in two deciduous forests, but similar data was not reported for coniferous forests in Japan. In Japanese forests, slope position is a key parameter controlling fine-root biomass that is greater on upper slopes than on lower slopes, probably because soil resource availability decreases upslope. Studies in manipulated soil environments (e.g., removing throughfall to simulate drought) also suggested that fine-root biomass and production were greatly affected by altered soil environments. Physiological control of fine-root dynamics was recently discussed via anatomical analyses of Chamaecyparis obtusa. Findings from Japanese studies generally support data on fine-root biomass and production obtained from other temperate regions. Further attempts to elucidate the influence of slope position (soil resource availability) on fine-root production would be useful to gain a more detailed understanding of the fine-root dynamics in Japanese forests.  相似文献   

2.
Root biomass and root distribution were studied in Entisols derived from the thick deposition of volcanic pumice on Hokkaido Island, Japan, to examine the effect of soil conditions on tree root development. The soil had a thin (<10 cm) A horizon and thick coarse pumiceous gravel layers with low levels of available nutrients and water. Two stands were studied: a Picea glehnii–Abies sachalinensis stand (PA stand) and a Larix kaempferi–Betula platyphylla var. japonica stand (LB stand). The allometric relationships between diameter at breast height (DBH) and aboveground and belowground biomass of these species were obtained to estimate stand biomass. The belowground biomass was small: 30.6 Mg ha−1 for the PA stand and 24.3 Mg ha−1 for the LB stand. The trunk/root ratios of study stands were 4.8 for the PA stand and 4.3 for the LB stand, which were higher than those from previous studies in boreal and temperate forests. All species developed shallow root systems, and fine roots were spread densely in the shallow A horizon, suggesting that physical obstruction by the pumiceous layers and their low levels of available water and nutrients restricted downward root elongation. The high trunk/root ratios of the trees may also have resulted from the limited available rooting space in the study sites.  相似文献   

3.
The distribution of fine (<2 mm diameter) and small roots (2–20 mm diameter) was investigated in a chronosequence consisting of 9-year-old, 26-year-old, 82-year-old and 146-year-old European beech (Fagus sylvatica) stands. A combination of trench wall observations and destructive root sampling was used to establish whether root distribution and total biomass of fine and small roots varied with stand age. Root density decreased with soil depth in all stands, and variability appeared to be highest in subsoil horizons, especially where compacted soil layers occurred. Roots clustered in patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size and number of root channels were comparable in all stands, and high values of soil exploitation occurred throughout the entire chronosequence. Overall fine root biomass at depths of 0–120 cm ranged from 7.4 Mg ha−1 to 9.8 Mg ha−1, being highest in the two youngest stands. Small root biomass ranged from 3.6 Mg ha−1 to 13.3 Mg ha−1. Use of trench wall observations combined with destructive root samples reduced the variability of these estimates. These records showed that variability in fine root distribution depended more on soil depth and edaphic conditions than on stand age, and suggest that trench wall studies provide a useful tool to improve estimates of fine root biomass.  相似文献   

4.
Fine roots play a key role in carbon and nutrient dynamics in forested ecosystems. Fine-root dynamics can be significantly affected by forest management practices such as thinning, but research on this topic is limited. This study examined dynamics of fine roots <1 mm in diameter in a 10-year-old stand of hinoki cypress (Chamaecyparis obtusa) for 3 years following thinning (65% in basal area). Fine-root production and mortality rates were estimated using a minirhizotron technique in combination with soil coring. In both thinned and un-thinned control plots, fine-root elongation occurred from early spring to winter (March to December) and fluctuated seasonally. In the thinned and the control plots, the annual fine-root production rates were estimated to be 101 and 120 g m−2 year−1, respectively, whereas the estimated annual fine-root mortality rates were 77 and 69 g m−2 year−1, respectively. At 3 years after thinning, live fine-root biomass was significantly smaller in the thinned plot (143 g m−2) than in the control plot (218 g m−2), whereas dead fine-root biomass was not (147 and 103 g m−2, respectively). Morphological and physiological indices of fine roots such as diameter, specific root length, and root tissue density of the live fine roots was similar in both plots. These results suggested that thinning tended to decrease biomass and production of fine roots, but the effects on characteristics of fine roots would be less evident.  相似文献   

5.
The responses of fine root mass, length, production and turnover to the increase in soil N availability are not well understood in forest ecosystems. In this study, sequential soil core and ingrowth core methods were employed to examine the responses of fine root (≤1 mm) standing biomass, root length density (RLD), specific root length (SRL), biomass production and turnover rate to soil N fertilization (10 g N m−2 year−1) in Larix gmelinii (larch) and Fraxinus mandshurica (ash) plantations. N fertilization significantly reduced fine root standing biomass from 130.7 to 103.4 g m−2 in ash, but had no significant influence in larch (81.5 g m−2 in the control and 81.9 g m−2 in the fertilized plots). Similarly, N fertilization reduced mean RLD from 6,857 to 5,822 m m−2 in ash, but did not influence RLD in larch (1,875 m m−2 in the control and 1,858 m m−2 in the fertilized plots). In both species, N fertilization did not alter SRL. Additionally, N fertilization did not significantly alter root production and turnover rate estimated from sequential soil cores, but did reduce root production and turnover rate estimated from the ingrowth core method. These results suggested that N fertilization had a substantial influence on fine root standing biomass, RLD, biomass production and turnover rate, but the direction and magnitude of the influence depended on species and methods.  相似文献   

6.
The biomass and the spatial distribution of fine and small roots were studied in two Japanese black pine (Pinus thunbergii Parl.) stands growing on a sandy soil. More biomass of fine and small roots was found in the 17-year-old than in the 40-year-old stand. There were 62 g m−2 of fine roots and 56 g m−2 of small roots in the older stand, which represented mean values of 608 g for fine and 552 g for small roots per tree, respectively. In the younger stand, a total of 85 g m−2 of fine roots and 66 g m−2 of small roots were determined, representing a mean of 238 g for fine and 186 g for small roots per tree, respectively. Fine and small root biomasses decreased linearly with a soil depth of 0–50 cm in the older stand. In the younger stand, the fine and small roots developed only up to a depth of 30 cm. Horizontal distributions (with regard to distance from a tree) of both root groups were homogeneous. A positive correlation in the amount of biomass of fine and small roots per m2 relative to tree size was found. Fine and small root biomasses increased consistently from April to July in both stands. The results also indicated earlier growth activity of the fine roots than small roots at the beginning of the growing season. The seasonal increases in fine and small root biomasses were slightly higher in the younger stand than the older stand.  相似文献   

7.
We assessed the influence of stand age on fine root biomass and morphology of trees and understory vegetation in 10-, 30-, 60- and 120-year-old Norway spruce stands growing in sandy soil in southeast Norway. Fine root (< 1, 1-2 and 2-5 mm in diameter) biomass of trees and understory vegetation (< 2 mm in diameter) was sampled by soil coring to a depth of 60 cm. Fine root morphological characteristics, such as specific root length (SRL), root length density (RLD), root surface area (RSA), root tip number and branching frequency (per unit root length or mass), were determined based on digitized root data. Fine root biomass and morphological characteristics related to biomass (RLD and RSA) followed the same tendency with chronosequence and were significantly higher in the 30-year-old stand and lower in the 10-year-old stand than in the other stands. Among stands, mean fine root (< 2 mm) biomass ranged from 49 to 398 g m(-2), SLR from 13.4 to 19.8 m g(-1), RLD from 980 to 11,650 m m(-3) and RSA from 2.4 to 35.4 m(2) m(-3). Most fine root biomass of trees was concentrated in the upper 20 cm of the mineral soil and in the humus layer (0-5 cm) in all stands. Understory fine roots accounted for 67 and 25% of total fine root biomass in the 10- and 120-year-old stands, respectively. Stand age had no affect on root tip number or branching frequency, but both parameters changed with soil depth, with increasing number of root tips and decreasing branching frequency with increasing soil depth for root fractions < 2 mm in diameter. Specific (mass based) root tip number and branching density were highest for the finest roots (< 1 mm) in the humus layer. Season (spring or fall) had no effect on tree fine root biomass, but there was a small and significant increase in understory fine root biomass in fall relative to spring. All morphological characteristics showed strong seasonal variation, especially the finest root fraction, with consistently and significantly higher values in spring than in fall. We conclude that fine root biomass, especially in the finest fraction (< 1 mm in diameter), is strongly dependent on stand age. Among stands, carbon concentration in fine root biomass was highest in the 30-year-old stand, and appeared to be associated with the high tree and canopy density during the early stage of stand development. Values of RLD and RSA, morphological features indicative of stand nutrient-uptake efficiency, were higher in the 30-year-old stand than in the other stands.  相似文献   

8.
Drought stress was simulated in a 28-year-old Japanese cedar plantation (Kanto Plain, Japan) between April and October 2004 by removing throughfall using rain shelters. Changes in fine-root parameters caused by this drought treatment were examined by sequential soil coring. Drought effects on fine roots were analyzed separately for particular soil depths (0–5, 5–15, and 15–25 cm) and root diameters (<1 and 1–2 mm). Generally, fine-root biomass and root tip numbers decreased by the drought treatment. Drought stress was most intense for fine roots in the topsoil and weakest for fine roots in the deepest soil layer. Fine roots less than 1 mm in diameter were affected more severely than 1- to 2-mm roots. The effect of drought treatment was most remarkable for the number of white root tips, which decreased to 17% of the control at the soil depth of 0–5 cm. These results suggest that white root tip is the most suitable indicator of drought stress. Simulated drought reduced production of fine roots less than 1 mm and 1–2 mm in diameter. Fine-root mortality was stimulated for roots less than 1 mm, but not for 1- to 2-mm roots. These results suggest that fine roots with larger diameters can survive drought stress at a level simulated in this study, but processes of fine-root production were inhibited regardless of the diameter classes. The duration of drought stress and phenology of fine roots should also be considered in diagnosing the effects of drought on fine-root parameters.  相似文献   

9.
Monitoring of soil nitrogen (N) cycling is useful to assess soil quality and to gauge the sustainability of management practices. We studied net N mineralization, nitrification, and soil N availability in the 0 10 cm and 11 30 cm soil horizons in east China during 2006 2007 using an in situ incubation method in four subtropical evergreen broad-leaved forest stands aged 18-, 36-, 48-, and 65-years. The proper- ties of surface soil and forest floor varied between stand age classes. C:N ratios of surface soil and forest floor decreased, whereas soil total N and total organic C, available P, and soil microbial biomass N increased with stand age. The mineral N pool was small for the young stand and large for the older stands. NO 3 - -N was less than 30% in all stands. Net rates of N mineralization and nitrification were higher in old stands than in younger stands, and higher in the 0 10 cm than in the 11 30 cm horizon. The differences were significant between old and young stands (p < 0.031) and between soil horizons (p < 0.005). Relative nitrification was somewhat low in all forest stands and declined with stand age. N trans- formation seemed to be controlled by soil moisture, soil microbial bio- mass N, and forest floor C:N ratio. Our results demonstrate that analyses of N cycling can provide insight into the effects of management distur- bances on forest ecosystems.  相似文献   

10.
We present results of individual-based root system measurement and analysis applied for Larix gmelinii trees growing on the continuous permafrost region of central Siberia. The data of root excavation taken from the three stands were used for the analyses; young (26 years old), mature (105 years old), and uneven-aged over-mature stand (220 years old). In this article, we highlight two topics: (1) factors affecting spatio-temporal pattern of root system development, and (2) interactions between aboveground (i.e., crown) and belowground (i.e., root) competition. For the first topic, the detailed observation of lateral roots was applied to one sample tree of the overmature stand. The tree constructed a superficial (<30 cm in depth) and rather asymmetric root system, and each lateral root expanded mainly into elevated mounds rather than depressed troughs. This indicated that spatial development of an individual root system was largely affected by microtopography (i.e., earth hummocks). For these lateral roots, elongation growth curves were reconstructed using annual-ring data, and annual growth rates and patterns were compared among them. The comparison suggested that temporal root system development is associated with differences in carbon allocation among the lateral roots. For the second topic, we examined relationships between individual crown projection area (CA) and horizontal rooting area (RA) for the sample trees of each stand. RA was almost equal to CA in the young stand, while RA was much larger (three or four times) than CA in the mature and overmature stands. Two measures of stand-level space occupation, crown area index (aboveground: CAI; sum of CAs per unit land area) and rooting area index (belowground: RAI; sum of RAs), were estimated in each stand. The estimates of RAI (1.3–1.8 m2 m−2) exceeded unity in all stands. In contrast, CAI exceeded unity (1.3 m2 m−2) only in the young stand, and was much smaller (<0.3 m2 m−2) in the two older stands. These between-stand differences in RAI–CAI relationships suggest that intertree competition for both aboveground and belowground spaces occurred in the young stand, but only belowground competition still occurred in the two older stands. Based on this finding, we hypothesized that competition below the ground may become predominant as a stand ages in L. gmelinii forests. Methodological limitations of our analysis are also discussed, especially for the analysis using the two indices of space occupation (CAI, RAI).  相似文献   

11.
 We evaluated the protective effects of floor cover against soil erosion in three types of forest located on steep slopes under a humid climate: 22- and 34-year-old Chamaecyparis obtusa (hinoki), 34-year-old Cryptomeria japonica (sugi), and 62-year-old Pinus densiflora (red pine) stands. We measured sediment transport rates (sediment mass passing through one meter of contour width per millimeter of rainfall), using sediment traps, before and after removing floor cover. Raindrop splash erosion was dominant in the experimental stands. Floor cover percentage (FCP) during the preremoval stage varied from 50% to 100% among the four stands, and sediment transport rates ranged from 0.0079 to 1.7 g m−1 mm−1. The rates increased to 1.5–5.6 g m−1 mm−1 immediately after removing floor cover, and remained high throughout the experiment. The presence of physical cover near the ground has a crucial effect on sediment transport on forested slopes. The protective effect ratio (the ratio of the sediment transport rate in a control plot to that in the removal plot) in a young hinoki stand, in which the FCP decreased markedly, was 0.3 at most, which is close to the rate for bare ground. The protective effect ratio in the red pine stand was ≤0.003. We concluded that the protective effect of floor cover in undisturbed forests in Japan differs by over two orders of magnitude, based on comparisons with previous studies. Received: March 11, 2002 / Accepted: August 16, 2002 Present address: Department of Forest Site Environment, Forestry and Forest Products Research Institute, Ibaraki 305-8687 Japan Tel. +81-298-73-3211; Fax +81-298-74-3720 e-mail: miura@affrc.go.jp Present address: Department of Forest Site Environment, Forestry and Forest Products Research Institute, Ibaraki 305-8687 Japan Tel. +81-298-73-3211; Fax +81-298-74-3720 e-mail: miura@affrc.go.jp Acknowledgments This study was supported by the Research Council of the Ministry of Agriculture, Forestry, and Fisheries, of Japan. We thank H. Ujihara, S. Ujihara, and M. Ogasawara in Otoyo, Kochi, who provided the experimental stands used in this study. We also thank K. Hirai, S. Kuramoto, E. Kodani, and the rest of the staff at the Shikoku Research Center, Forestry and Forest Products Research Institute, for their help in conducting the experiments. Correspondence to:S. Miura  相似文献   

12.
以徐州林场50年生侧柏人工林为研究对象,采用挖掘法获取土壤根系样品,探究林分密度对侧柏人工林不同根序细根形态的影响。结果表明:细根的直径和根长随着根序上升而显著增大,而比根长则随着根序的上升而显著减小。低林分密度(1 679株/hm2)与中林分密度(2 250株/hm2)相比显著减小了表层土壤1、2级细根的平均直径和平均根长,亚表层土壤3级细根的根长,显著增大了亚表层土壤2级细根的平均比根长;高林分密度(3074株/hm2)比中林分密度显著增大了2级根的平均比根长。与高林分密度相比,低林分密度显著减小了表层土壤1、2级细根的平均直径,增大了亚表层土壤5级细根的平均直径。  相似文献   

13.
杉木纯林、混交林土壤微生物特性和土壤养分的比较研究   总被引：6，自引：0，他引：6  
王清奎  汪思龙 《林业研究》2008,19(2):131-135
本文于2005年5月份,在中国科学院会同森林生态实验站选择了一块15年生的杉木纯林和两块15年生杉阔混交林作为研究对象,调查了林地土壤有机碳、全氮、全磷、硝态氮、有效磷和土壤微生物碳、氮、磷、基础呼吸以及呼吸熵,比较了纯林和混交林土壤微生物特性和土壤养分.结果表明,杉阔混交林的土壤有机碳、全氮、全磷硝态氮和有效磷含量高于杉木纯林;在混交林中,土壤微生物学特性得到改善.在0(10 cm和10(20 cm两层土壤中,杉阔混交林土壤微生物氮含量分别比杉木纯林高69%和61%.在0(10 cm土层,杉阔混交林土壤微生物碳、磷和基础呼吸分别比杉木纯林高11%、14%和4%;在10(20 cm土层,分别高6%、3%和3%.但是,杉阔混交林土壤微生物碳:氮比和呼吸熵较杉木纯林低34%和4%.另外,土壤微生物与土壤养分的相关性高于土壤呼吸、微生物碳:氮比和呼吸熵与土壤养分的相关性.由此可知,在针叶纯林中引入阔叶树后,土壤肥力得以改善,并有利于退化森林土壤的恢复.  相似文献   

14.
Most Eucalyptus plantations are intensively managed as short-rotation plantations and carbon (C) storage in plants and soils in stands older than 10 years is not well understood. We examined the changes in plant biomass C and soil organic C (SOC) storage across a chronosequence of E. urophylla × E. grandis forests (4-, 7-, 10-, 13-, and 21-year-old) in subtropical China. Biomass C stock significantly increased with stand age. SOC storage increased initially after afforestation, peaking in 10-year-old stands, and declined gradually. Ecosystem C pools in the five development stages were 111.76, 167.66, 234.04, 281.00, and 299.29 Mg ha?1, respectively. Trees and soils were the dominant C pools across all stand ages with the contribution of tree biomass C storage significantly increasing and SOC storage decreasing with age. Eucalyptus plantations are still in vigorous growth phase and have great potential for C sequestration at the end of the current rotation length (within 7 years). Considering the sharp decrease of annual biomass C increment rate and the gradual loss of SOC storage in stands older than 13 years, we recommend the optimal length for one full Eucalyptus plantation cycle should be 12–15 years in subtropical China to maximize land-use value and carbon sink value.  相似文献   

15.
Tree roots in a changing world   总被引：1，自引：0，他引：1  
Globally, forests cover 4 billion hectares or 30% of the Earth's land surface, and 20%–40% of the forest biomass is made up of roots. Roots play a key role for trees: they take up water and nutrients from the soil, store carbon (C) compounds, and provide physical stabilization. Estimations from temperate forests of Central Europe reveal that C storage in trees accounts for about 110 t C ha−1, of which 26 t C ha−1 is in coarse roots and 1.2 t C ha−1 is in fine roots. Compared with soil C, which is about 65 t C ha−1 (without roots), the contribution of the root C to the total belowground C pool is about 42%. Flux of C into soils by plant litter (stemwood excluded) compared with the total soil C pool, however, is relatively small (4.4 t C ha−1 year−1) with the coarse and fine roots each contributing about 20%. Elevated CO2 concentrations and N depositions lead to increased plant biomass, including that of roots. Recent analysis in experiments with elevated CO2 concentrations have shown increases of the forest net primary productivity by about 23%, and, in the case of poplars, an increase of the standing root biomass by about 62%. The turnover of fine roots is also positively influenced by elevated CO2 concentrations and can be increased in poplars by 25%–45%. A recently established international platform for scientists working on woody root processes, COST action E38, allows the exchange of information, ideas, and personnel, and it has the aim to identify knowledge gaps and initiate future collaborations and research activities.  相似文献   

16.
Fine roots are a key component of forested ecosystems, but available information is still limited. This study examined the production and mortality of fine roots less than 1 mm in diameter in a Japanese cedar (Cryptomeria japonica D. Don) plantation located on the Kanto Plain in central Japan. We used a minirhizotron technique in combination with soil coring, and collected data for 1 year (May 2002–May 2003). Fine root production and mortality were determined from changes in the lengths of individual fine roots on minirhizotron tubes. Both fine root production and mortality rates were greater in the upper soil than in lower soil levels. Both rates were seasonal, with higher values in summer than in winter; this trend was more pronounced in upper soil levels. These results suggest that environmental conditions, such as temperature or soil properties, affect the production and mortality rates of fine roots. Fine root production and mortality occurred simultaneously, and their rates were similar, which may have led to unclear seasonal changes in fine root standing crop estimates. Soil coring indicated that the fine root biomass of this stand was about 120 g m−2, of which 40% was from Japanese cedar. The estimated rates of dry matter production and mortality of total fine roots, including understory plants, were both approximately 300 g m−2 year−1.  相似文献   

17.
We investigated the Effects of plantation development, seasons, and soil depth on soil microbial indices in Gmelina arborea plantations in south-western Nigeria. Soil samples were obtained from the soil depths of 0-15 and 15-30 cm from plantations of six different ages during the rainy season, dry seasons, and their transitions. We used plate count and fumigation-extraction methods to determine microbe population and microbial biomass carbon (MB-C) and nitrogen (MB-N), respectively. Plantation age did not affect microbial indices, implying a non-significant effect of plantation development on microbial communities. It could also imply that soil microbial indices had already stabilized in the sampled plantations. Seasonal variation and soil depth had significant effects on microbial indices. At 0-15 cm soil depth, mean MB-C increased from 50.74 μg g-1 during the peak of the dry season (i.e. March) to 99.58 μg g-1 during the peak of the rainy season (i.e. September), while it increased from 36.22 μg g-1 to 75.31 μg g-1 at 15-30 cm soil depth between the same seasonal periods. Bacteria populations and MB-N showed similar increasing trends. Correlations between MB-C, MB-N, microbe populations, and rainfall were positive and linear. Significantly higher microbial activities took place in the plantations during the rainy season, increased with soil wetness, and decreased at greater soil depth.  相似文献   

18.
[目的]以云南省普洱市主要植被思茅松人工林为研究对象,探讨不同林龄思茅松人工林根系生物量的大小分布及变化特征。[方法]分别在5、8、15、25、36年生思茅松人工林内,利用内径为8.5 cm的根钻分3层(0~10、10~20、20~30 cm)获取思茅松与其它物种的细根、粗根及死根生物量数据。[结果]表明:随着思茅松人工林林龄的增长,思茅松细根生物量呈减少的趋势,而其它物种细根生物量呈增加趋势,细根生物量最大出现在36年生思茅松人工林。不同林龄思茅松人工林的思茅松粗根和死根生物量之间无显著差异,而其它物种及林分的粗根生物量和根系生物量则随林龄增长而增加。思茅松人工林的细根生物量主要分布在土壤深度0~10 cm内,其中,思茅松、其它物种、林分细根生物量以及根系生物量随土层深度的增加呈减少趋势。林龄和土壤深度对思茅松与其它物种的细根生物量有显著影响,林龄与土壤深度的交叉作用对思茅松细根生物量有显著影响,林龄对死根生物量有显著影响,林龄、土壤深度及林龄与土壤深度的交叉作用对粗根与根系的生物量有显著影响。[结论]思茅松人工林随着林龄增长,群落结构与树种组成随之发生变化,从而对根系生物量产生较大影响。  相似文献   

19.
Although afforestation of farmlands has been proposed as an effective method of carbon (C) sequestration, there remain uncertainties that deter us from developing a clear picture of C stocks in plantation ecosystems. This study investigated the dynamics of stand structure and plant diversity, and C and nitrogen (N) pools in trees, herbs, litter, and soil (0–100 cm depth) in black locust plantations aged 9, 17, 30, and 37 years, and in newly abandoned farmlands as pre-afforestation sites, on the Loess Plateau, China. Stand density decreased significantly, while tree diameter at breast height and height increased during stand development. The dominant species of the herb layer differed with age. Afforestation resulted in slight increases in tree C and N storage in plantations from 9 to 30 years of age, and then significantly increased from 30 to 37 years. Compared to pre-afforestation, C and N storage in soil decreased to minimum values in stands aged 17 and 9 years, respectively. The soil re-accumulated C and N during stand development, attaining equilibrium levels similar to those in pre-afforestation when stands reached about 30 years of age. Soil C and N storage in 37-year stands were 29 and 16% higher, respectively, than in pre-afforestation levels. However, C and N concentrations in the subsoil (20–40 cm) were still less than the pre-afforestation levels for stands of all ages (from 9 to 37 years). The relative contribution to the total ecosystem C and N pools increased in trees and decreased in soil during the observed period. Our results indicate that afforestation reduced soil C and N storage during the early stages of stand development. We conclude that the growing phase of an afforested stand over its initial 30 years is important for C and N sequestration by black locust due to the C and N storage that result from recovered soil quality and an increase in tree biomass.  相似文献   

20.
We investigated age-related changes in biomass cycling and soil properties in a kayu putih (Melaleuca leucadendron LINN, Myrtaceae) with improved shifting cultivation system in East Java, Indonesia, to design better management plans for sustainable kayu putih oil production and crop yield. Harvested biomass of kayu putih increased markedly from 7- to 15-year-old stands, but did not increase further in older stands averaging 2.41 Mg ha−1 yr−1. Kayu putih contributed 1.9–31.0% of total biomass production. Cassava (Manihot esculenta Crantz) tuber was the largest component of biomass cycling. Harvested biomass of cassava decreased with increasing stand age and there was a trade-off between above- and below-ground biomass productions. Harvested biomass of maize (Zea mays L.) grain was constant throughout stand growth, whereas returned biomass fluctuated. With increasing stand age, soil organic matter (SOM) accumulated in soil indicating that returned biomass was decomposing slowly. Content of primary nutrients did not change with stand age. The contribution of cassava to harvested biomass was considerably larger than that of kayu putih. For this reason, selection of cassava as a single companion crop may not be suitable for sustaining kayu putih oil production. Maize may be a good companion crop for kayu putih because it produces a constant grain yield throughout stand growth and its contribution to harvested biomass is comparable to that of kayu putih. In addition, maize is shallow-rooted and causes less below-ground competition with deep-rooted kayu putih trees.  相似文献   

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