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71.
72.
Forage and wood yield of Acacia cyanophylla, also known as Acacia saligna, was studied in a 300–400 mm precipitation zone in Tunisia. Yields were measured during and after drought. This short (2–8
m) evergreen leguminous tree is used as a forage drought reserve in frost free regions where mean annual precipitation exceeds
250 mm. The standing crop of leafy forage builds up year after year for at least four years or until the tree is cut. It rapidly
regrows after cutting from coppice shoots. The leaves provide high protein forage for sheep and goats during the long dry
summer season typical of the Mediterranean climate as well as emergency forage during drought. The tree is used to stabilize
moving sand dunes, and as a windbreak to protect cropland. It also provides fuelwood and increasaes soil nitrogen by fixation.
The need for supplemental irrigation during establishment is a major constraint.
Research in the 350 mm precipitation zone of Tunisia found 3.2 year old trees to yield over 1400 kg of forage standing crop
per hectare after a severe drought. Trees harvested at 2.5 years of age in May, during the worst drought in over 30 years,
yielded a standing forage crop of 724 kg per hectare. Forage regrowth 8 months after cutting and 4 months after rains returned
was 700 kg/ha. The forage standing crop for trees harvested only once during the 3.2 year period was double the amount of
forage regrowth from trees harvested the previous year, but mean annual forage yield similar. This demonstrates that it is
possible for forage to be conserved as a living forage reserve for later use during drought. Total wood yield was only 1621
kg/ha for trees cut twice compared to 3683 kg/ha for trees cut only once.
Annual cutting will substantially reduce the amount of forage available during drought and reduce the production of fuelwood.
It may also reduce the vigor, productivity and life of the tree. Acacia cyanophylla alley cropped on cereal farmland can protect the soil from erosion, protect the associated crop from wind damage, fix nitrogen,
provide fuelwood and provide a reserve of high quality forage for use during drought.
This work was supported by the Government of Tunisia and the U.S.A.I.D. Tunisia Range Development and Management Project (664-0312.8). 相似文献
73.
74.
对湘西女儿寨流域不同植被恢复类型的土壤结构特征研究和健康评价的结果表明:荒草灌丛容重最高,人工林土壤容重高于天然林及混交林;对土壤孔隙状况的改善作用表现为林分类型优于荒草灌丛类型,天然林优于人工林,0~20 cm土层优于20~40 cm土层;土壤团聚体平均重量直径以油桐人工林、杜仲人工林最高,马尾松天然林、毛竹杉木混交林其次,而润楠次生林、荒草灌丛、杉木人工林较低;各层土壤团聚体分形维数值大小排序为:毛竹杉木混交林>马尾松天然林>荒草灌丛、润楠次生林>杜仲人工林>油桐人工林>杉木人工林;土壤结构健康综合评价的灰色关联分析结果表明,土壤结构以荒草灌丛最差,油桐人工林最好,其余类型介于两者之间.研究结果可为女儿寨流域及我国类似生态脆弱区的植被恢复与重建提供一定依据和参考. 相似文献
75.
76.
在人工气候箱内设7个温度处理松白粉蚧成虫,9个温度处理松白粉蚧卵。结果表明:温度对松白粉蚧越冬代成虫死亡率、产卵量、卵孵化率有显著影响。卵的发育起点温度约为13℃,有效积温为456.7日度,发育最适温度在25℃左右;在21~27℃时,卵的孵化率在90%以上,差异不显著,但在33~36℃,卵几乎不孵化,用线性日度模型、王氏模型与Logistic模型对卵的发育速率进行拟合,均有较好的相关性和拟合度。试验结果与野外试验得出的结论基本一致:高温是新侵入地区松白粉蚧夏季种群数量显著下降的原因之一。 相似文献
77.
The beneficial effect of organic matter on soil aggregate stability is well documented. Alley cropping has been suggested as a possible alternative to maintain soil organic matter content in cropping systems without fallowing the land. The objective of this study was to asses the effect of alley cropping on dry and wet soil aggregate stability on land degraded by shifting cultivation. The aggregate size distribution by dry sieving, aggregate stability by wet sieving, soil organic Carbon content and soil bulk density were measured following two and three years of alley cropping with Gliricedia (Gliricidia sepium) and Pigeon pea (Cajanas cajan) in a tropical Rhodustalf. Alley cropping increased the mean aggregate diameter and water stability of soil aggregates. The mean aggregate diameter obtained from dry sieving increased from 1.3 mm of the control to 2.68 and 3.11 mm after three years in Pigeon pea and Gliricidia alley cropped plots, respectively. This is an indication of resistance to wind erosion in alley cropped plots. The wet aggregate stability which shows the resistance to erosion by water also increased in alley cropped plots. These increases were significant after three years of hedge row establishment. The increase in soil organic C in alley cropped plots contributed to the higher dry and wet aggregate stability, and decreased soil bulk density. The improvement was higher in plots alley cropped with Gliricidia than Pigeon pea. This study shows the importance of ally cropping in increasing aggregate stability of degraded sandy soils which in return reduce erosion by wind and water. 相似文献
78.
苦竹各器官主要营养元素分布及采伐的养分输出 总被引:3,自引:0,他引:3
本文根据四川长宁苦竹(Pleioblastus amarus)各器官生物量以及其主要营养元素含量和储量,研究了苦竹采伐的养分输出问题。结果表明:苦竹各器官中N、P、K、Si、Ca、Mg等6种营养元素以代谢旺盛的竹叶和竹鞭中含量最高;6种养分元素在各器官贮存量(单位:kg.hm-2)从大至小的排序为:叶(510.8)>竹根(230.62)>杆(182.14)>枝(163.77>竹鞭(59.19)>竹蔸(41.16)。苦竹采伐的养分年输出量(单位:kg.hm-2)从大至小的排序为:Si(50.23)>K(38.77)>N(35.58)>Mg(4.55)>P(3.86)>Ca(3.31)。对比该地区的降雨输入,苦竹林地养分以Si失衡最为严重;其次为K、N。若采伐时将竹叶带出竹林,6种元素的养分输出总量将增加1.48倍。可见,竹叶归还林地对维持地力具有极其重要的作用。 相似文献
79.
用比较分析法和多目标最优化法对不同的杨梅疏果量与投入、产量、产值、效益的关系进行比较、分析表明 :疏果措施可提高杨梅的品质 ,增加产值和收益 ,当疏果量达到 6 0 %时有最大的纯收益 ,疏果量达到 70 %时有最好的投资效果 ,6 0 %~ 70 %的疏果量是杨梅最佳疏果方案 相似文献
80.