Stand level estimation of root respiration for two subtropical plantations based on in situ measurement of specific root respiration

In this study, the stand level root respiration was estimated for two monoculture plantations: Acacia crassicarpa and Eucalyptus urophylla, based on in situ measurement of specific root respiration using simplified root chamber method. The respiration rates of fine roots (<5 mm) were significantly higher than those of coarse roots (>5 mm) for both A. crassicarpa and E. urophylla species. The root respiration of A. crassicarpa showed a clear seasonal pattern with a higher value in the wet season. For E. urophylla, the seasonal pattern was observed for fine roots but not for coarse roots. After determining the biomass of fine roots and coarse roots and their specific rates of respiration at different time points, root respiration at the stand level (R_a) was estimated using a direct up-scaling model. We found that the R_a accounted for 14% and 19% of total soil respiration (R_s) for A. crassicarpa and E. urophylla, respectively. The fine (R_Tf) and coarse (R_Tc) root respiration at the stand level accounted for about 47% and 53% of the R_a for A. crassicarpa, and accounted for 58% and 42% for E. urophylla. This suggests that coarse root respiration cannot be ignored when estimating the root respiration at the stand level. Our results showed that the Q₁₀ values were more accurate in representing the temperature dependence when the confounding effect of soil moisture was considered. This study introduces an alternative approach to estimate stand level root respiration, but its reliability is largely dependent on the accuracy of root biomass quantification.     

马占相思人工林生态系统养分积累与分配

通过对8年生马占相恩人工林生态系统养分积累与分配的研究,结果表明：林地土壤0-50cm土层内全c积累量为69090kg·hm^-2,全N积累量为3725kg·hm^-2,全P积累量为647kg·hm^-2,交换性K积累量为648kg·hm^-2,交换性Ca积累量为987kg·hm^-2,交换性Mg积累量为63kg·hm^-2;凋落物养分积累量N为58．764kg·hm^-2·a^-1,P积累量为1．608kg·hm^-2·a^-1,K积累量为9．021kg·hm^-2·a^-1,Ca积累量为22．898kg·hm-2·a^-1,Mg积累量为4．079kg·hm^-2·a^-1;人工林林分各元素积累量N为277．04kg·hm^-2、P为7．72kg·hm^-2、K为57．21kg·hm^-2、Ca为93．22kg·hm^-2、Mg为10．24kg·hm^-2;林下植被养分积累量N、P、K、Ca、Mg分别为35．40、2．67、29．47、22．38、4．00kg·hm^-2。     

大叶相思人工林木材理化特性及利用方式的研究

对同林龄不同林分大叶相思人工林木材试验地的生长量调查、化学组成测定及相关部位利用的研究 ,结果表明 :萌生林分比实生林分的材积和生物量分别提高 14 8%和 4 3 4 % ,证实速生树种形成次生林的幼树具有早期速生的特点 ;不同林分材性变化不明显 ,木材基本密度均≤ 0 .6 0g·cm- 3,纤维长度为 898～ 916μm ,壁腔比 0 5 6～ 0 6 0 (<1) ,纤维柔性系数 5 9 3～ 6 8 5 ,在 75～ 5 0范围内。采用KP法制浆 ,细浆得率达 4 4 %以上 ,木浆物理性能均达本色硫酸盐阔叶木浆标准 ;萌生林分鲜原胶产量大于实生林分 ,单株平均净增产鲜原胶 1 4 2kg ;挂胶与否对木材化学组成无影响而对树皮有影响 ,但不论挂胶与否 ,其树皮含单宁量高达 9 97%～ 11 4 0 % (>8% ) ,用于制备栲胶 ,产品质量及鞣革性能均优于国产一级木麻黄栲胶标准 ;木材、枝丫材作培养基栽培香菇等食用菌 ,其产量和生物效率与木屑对照组比较 ,均值差异达极显著 (F 相似文献   

Fruit infestation of Acacia tortilis (Forsk) hyne by Bruchidius andrewesi Pic. (Coleoptera: Bruchidae) in the Thar desert

Bruchidius andrewesi Pic. has been recorded as a serious pest of pods and seeds of Acacia tortilis in the Thar desert of India. Pest infestation on developing pods and its relationship with morphological traits is reported. Pod infestation varied from 5 to 19% with 5–29% infestation of seeds. Infestation of pods is directly related to infestation of seed (r = 0.72^**), and both pod and seed infestation are also directly correlated with loss in seed biomass (r = 0.79^** and R = 0.88^**). The infestation of pods starts in November and increases steady until harvest. Seeds kept in the laboratory for further studies were found to be 100% infested with B. andrewesi, as the insect multiplied faster under these conditions. The heavy infestation is damaging not only to A. tortilis but also to other leguminous trees of the desert. Bruchidius andrewesi has also been found on pods and seeds of Prosopis cineraria, an important indigenous tree of the region.     

城市污水污泥对马占相思和阴香生长的影响

研究在城市污水浇灌和半污泥栽培下,马占相思(Acacia mangium)和阴香(Cinnamomum burmanni)2种树种生长量和生物量变化情况。结果表明,半污水处理、全污水处理、半污泥处理均促进了马占相思的高生长量、地径生长量、生物量的增加,而阴香的增长量随着污水浓度的增加而降低,在半污泥处理下生长最差。表明马占相思具有较强的抗城市污水污泥污染能力,而阴香抗污染能力较差。     

桂西南地区黑木相思生长规律、生物量及生产力研究

采用标准地平均木树干解析法对桂西南地区9年生黑木相思人工林的生长规律、生物量、生产力进行研究,结果表明:黑木相思人工林树高、胸径的生长高峰期出现在2~4年生时,树高、胸径连年生长量与平均生长量相交年龄分别是在4、5年生,材积的数量成熟期在8年生以后。9年生时,胸径(带皮)、树高、单株材积、立木蓄积分别为14.9 cm、15.8 m、0.13368 m3、189.15 m3.hm-2;平均木单株各器官的生物量所占比例大小分别为树干枝根干皮叶,干材所占比例达到58.18%;乔木层总生物量为173.32 t.hm-2,净生产力为19.26 t.hm-2.a-1。     

滨海砂地厚荚相思人工林生长特性研究

经对闽南滨海砂地后缘引种的厚荚相思人工林生长特性研究表明 ,厚英相思在 2年生前生长较为缓慢 ,2a后生长迅速 ,其树高、胸径、材积连年生长高峰期分别出现在第 6年 ,第 3～ 6年间和第 7年 ,数量成熟期为 15年左右。在现行造林密度条件下 ,以纸浆材为培育目标 ,则轮伐期应为8～ 9年且不需要间伐     

Biocycle of nitrogen in a Cyclobalanopsis glauca-dominated evergreen broad-leaved forest in East China

The nitrogen (N) cycling was elucidated in a 40-year-old subtropical evergreen broad-leaved forest dominated by Cyclobalanopsis glauca growing on red soil in Zhejiang Province, East China. The concentrations of N in the representative species ranged from 0.49% to 1.64%, the order of which in various layers was liana and herb layers > understory layer > tree and subtree layers; in various organs was leaf > branch > root > trunk; and aboveground parts > underground parts. The sequence of the concentrations of N in C. glauca was understory > tree > subtree layer; young and high-growing > old organs; reproductive > vegetative organs. Seasonal dynamics of the concentrations of N in C. glauca in the tree and subtree layers was comparatively stable. It was lower in autumn (October) in root, branch, and leaf in the tree layer, and low in January in the understory. There was no evident change in regularity of the concentrations of N in varying diameter classes. The concentrations of N in the litterfall, precipitation, throughfall, litter layer, and soil were 0.74%–2.30%, 0.000,038%, 0.000,09%, 1.94%, and 0.59%, respectively. The standing crop of N in the plant community was 1,025.28 kg/hm², accumulation in the litter layer was 224.88 kg/hm², and reserve in the soil was 55,151 kg/hm². Annual retention of N was 119.47 kg/hm², return was about 84.13 kg/hm², among which litterfall was 78.49 kg/hm² and throughfall, 5.64 kg/hm². Annual absorption of N was 203.60 kg/hm². Annual input of N through incident precipitation was 4.88 kg/hm². Compared with other forest types, cycling rate of N in the community was lower than in deciduous broad-leaved forests, rain forests, and mangroves, and was moderate in evergreen broad-leaved forests. N use efficiency of this forest was moderate among the forest types cited. According to the characteristics of the biocycle of phosphorous, it was concluded that N availability in the soil of this forest was not lower, and phosphorous not N was the limiting factor in the growth of plants in this community. __________ Translated from Acta Ecologica Sinica, 2005, 25(4): 740–748 [译自: 生态学报, 2005, 25(4): 740–748]     

外来树种马占相思自然繁殖更新研究

调查马占相思人工林的自然更新情况,在国内首次发现马占相思存在种子成苗方式的自然更新.但马占相思的自然更新受立地条件制约:只有在林缘的裸露立地条件下,马占相思的种子才能萌发成苗.马占相思16年生单株在45°扇形单方向更新扩散的最远距离为17.5 m,更新繁殖的株数最多有26株;扩散距离与扩散株数之间没有明显的相关性.1987年穴状埋根造林的马占相思,其林缘更新扩散的最远距离为10.0 m,更新繁殖的株数最多有3株;1997年穴状埋根造林的马占相思,其林缘更新扩散的最远距离为3.0 m,更新繁殖的株数最多有14株.用小样方法调查马占相思人工林下乡土乔木、灌木和草本植物的自然更新.结果表明,在马占相思林分内,共发现12种乔木树种、3种灌木树种和8种草本植物,这些乡土植物均表现为生活力强.研究结果表明,马占相思在靠近水源的裸露立地条件下可以自然更新,更新的方式为种子繁殖;马占相思不影响乡土植物的正常生长.     

Evaluation of the fire endurance of mechanically graded timber in bending

AbstractThis study examined the performance of mechanically graded timber in bending when exposed to fire at various load ratios. The test specimens were 150 pieces, each with the dimensions of 60 × 120 × 3500mm. The modulus of elasticity (MOE) of 150 specimens was measured, and 60 among them were selected to formulate the prediction equation for MOE and modulus of rupture (MOR), which was used to predict the remaining 90 specimens. These were tested under fire exposure in bending using three-point loading at 11.1%, 16.7%, 33.3%, 66.7%, and 83.3% of the ultimate load. Using mechanically graded timber, which means acknowledging the actual strength of the bending member, permits fairly precise application to the targeted design load. This research confirmed that mechanically graded timber under fire exposure has the following tendencies: under the same load ratio, time to failure is independent of strength class, and, at any load ratio, the critical strength is dependent on the timber strength class. The obtained design bending strength under fire exposure using the reduced cross section method and the reduced strength method conformed to those calculated based on Eurocode 5. Following those findings, mechanically graded timber can be applied to obtain the design bending strength when taking into account the fire attack.