Background:Insect herbivory has profound impacts on ecosystem processes and services.Although many efforts have been made to recognize the main drivers of insect herbivory at different scales,the results are inconsist...Background:Insect herbivory has profound impacts on ecosystem processes and services.Although many efforts have been made to recognize the main drivers of insect herbivory at different scales,the results are inconsistent.One likely reason is that studies have insufficiently captured the spatially heterogeneous factors such as soil type and forest stratum within the stand that may significantly affect insect herbivory.In particular,there is a lack of studies that address the detailed spatial patterns of insect herbivory which are influenced by these factors.Methods:We measured the detailed spatial patterns of insect herbivory on cork oak(Quercus variabilis Bl.)in response to soil type(gravel soil and loam)and forest stratum(the upper,lower,and sapling stratum),and correlated these patterns with a set of influencing factors(litter coverage,coverage of shrubs and herbs,soil nutrients,soil moisture,and leaf traits)in a forest landscape.Results:Generally,insect herbivory was spatially heterogeneous within stands.Herbivory was significantly lower in gravel soil areas than in loam soil areas and the highest herbivory occurred in the lower stratum.However,there were also 41 individual plots in which the highest herbivory occurred in the upper stratum and 29 plots in which the highest herbivory occurred in the sapling stratum.There were significant differences in soil nutrient and water status between soil types,but no significant differences in leaf traits.The effects of forest stratum on leaf traits were also inconsistent with those on insect herbivory.Conclusions:Leaf traits may not be the main factors influencing insect herbivory in the field.Soil type may have major effects on herbivory patterns by influencing litter coverage while higher coverage of shrubs and herbs may reduce herbivory in the sapling stratum.These findings may advance our understanding of tree-herbivore interactions in real-world situations and have important implications for the sustainable management of forest ecosystems.展开更多
The scale of forest and landscape restoration is expected to increase during the UN Decade on Ecosystem Restoration and its contribution to the provision of critical ecosystem services to society.Several models of for...The scale of forest and landscape restoration is expected to increase during the UN Decade on Ecosystem Restoration and its contribution to the provision of critical ecosystem services to society.Several models of forest restoration may improve ecosystem services,including soil organic carbon(SOC)storage.A review was carried out to access:(1)the variability of SOC storage between worldwide forest restoration models and,(2)the effects of climate,soil class,soil texture,and vegetation type on SOC storage.We reviewed 119 primary studies with information on SOC and soil texture for different forest restoration models.The restoration models were grouped into four categories:natural regeneration,monocultures,agroforestry,and mixed forest.SOC data was extracted from these four restoration models,other land uses(cropland,bare land,grassland,and natural forest),climate regimes,and soil properties.The SOC storage in the forest restoration models and other land uses at a global scale ranged between 0.1 to 514 Mg ha^(-1).The overall mean value for SOC storage was higher for natural regeneration(112 Mg ha^(-1)),followed by agroforestry(74 Mg ha^(-1)),mixed forest(73 Mg ha^(-1)),and monocultures(68 Mg ha^(-1)).However,the average SOC storage was similar among the four restoration models in the moist warm climate zone.The SOC storage mean value in the moist cool zone was 23%higher than the dry cool zone(81 and 62 Mg ha^(-1),respectively),and 50%higher for the moist warm zone when compared to the dry warm climatic zone(74 and 38 Mg ha^(-1),respectively).The SOC storage of the restoration models was positively related to soil depth(0.59;p<0.01),clay content(0.29;p<0.01),and stand age(0.17;p<0.01).Globally,the mean values of SOC storage were 26,66,and 139 Mg ha^(-1) at zero-10,zero-30,and zero-100 cm depths,respectively.In addition,sandy soils showed smaller mean values of SOC storage than medium to clay soils,especially in deeper soil layers.Furthermore,SOC storage was positively related between restoration models and other land uses(0.93;p<0.01),suggesting a prominent effect of climate and soil properties on SOC.Forest restoration models showed larger SOC storage when compared to croplands and bare land,but in general it was smaller or similar when compared to pasture and natural forest.展开更多
The variation in shoot and root seedling growth traits was compared among three Faidherbia albida （Del）. A. Chev. provenances originating from Kenya （Taveta）, Malawi （Bolero） and Ghana （Bolgatanga）; representi...The variation in shoot and root seedling growth traits was compared among three Faidherbia albida （Del）. A. Chev. provenances originating from Kenya （Taveta）, Malawi （Bolero） and Ghana （Bolgatanga）; representing east, south and west Africa, respectively. Bulked seeds from three provenances were grown in two soil types （clay and sand） at the World Agroforestry Centre nursery, Nairobi. Seedlings grown in clay soil had high shoot growth and shoot to root ratios but shorter root length, lower number of nodules and specific root length compared to seedlings in sand soil. Shoot to root ratios reduced with time and this was more pronounced in sand soil. Overall, the Bolero and Taveta provenances had higher growth than the Bolgatanga provenance. This was probably because plants grown in nutrient-rich clay soil invest more in shoot growth as compared to root growth. Longer root growth in sand soil shows a better adaptive mechanism that increases competitive ability and survival in nutrient-poor systems. Variations observed among the seedling variables such us shoot and root growth could be used for early selection for reforestation and agroforestry in predominantly clay and sand soil areas.展开更多
Small H-beams such as the No.14-20 I-steel can be inserted into soil-cement retaining walls to form small H-beam soil-cement compound walls, functioning both as a retaining wall and a cutoff wall for braced structure ...Small H-beams such as the No.14-20 I-steel can be inserted into soil-cement retaining walls to form small H-beam soil-cement compound walls, functioning both as a retaining wall and a cutoff wall for braced structure excavations. Being different from the mixed soil-cement wall （SMW）, the interaction between soil-cement and small H-steel is very good. We have carried out a series of bending experiments on small H-beams in soil-cement model compound beams to study the mechanism of interactions. The results show that the interaction between H-beams and soil-cement is very good, whether the H-beam is single or double. Joint forms of double H-beams at one end have little effect on both the contribution coefficient and on ultimate deflection before cracking. But after cracking, the joint forms greatly affect the contribution coefficient. We conclude that the rigid joint girder for double H-beams is a better choice in oractice.展开更多
基金supported by the National Key Research and Development Project of China(2018YFD060024-04).
文摘Background:Insect herbivory has profound impacts on ecosystem processes and services.Although many efforts have been made to recognize the main drivers of insect herbivory at different scales,the results are inconsistent.One likely reason is that studies have insufficiently captured the spatially heterogeneous factors such as soil type and forest stratum within the stand that may significantly affect insect herbivory.In particular,there is a lack of studies that address the detailed spatial patterns of insect herbivory which are influenced by these factors.Methods:We measured the detailed spatial patterns of insect herbivory on cork oak(Quercus variabilis Bl.)in response to soil type(gravel soil and loam)and forest stratum(the upper,lower,and sapling stratum),and correlated these patterns with a set of influencing factors(litter coverage,coverage of shrubs and herbs,soil nutrients,soil moisture,and leaf traits)in a forest landscape.Results:Generally,insect herbivory was spatially heterogeneous within stands.Herbivory was significantly lower in gravel soil areas than in loam soil areas and the highest herbivory occurred in the lower stratum.However,there were also 41 individual plots in which the highest herbivory occurred in the upper stratum and 29 plots in which the highest herbivory occurred in the sapling stratum.There were significant differences in soil nutrient and water status between soil types,but no significant differences in leaf traits.The effects of forest stratum on leaf traits were also inconsistent with those on insect herbivory.Conclusions:Leaf traits may not be the main factors influencing insect herbivory in the field.Soil type may have major effects on herbivory patterns by influencing litter coverage while higher coverage of shrubs and herbs may reduce herbivory in the sapling stratum.These findings may advance our understanding of tree-herbivore interactions in real-world situations and have important implications for the sustainable management of forest ecosystems.
基金the World Resources Institute for the financial supportthe Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)for fellowships of the first author(Process Numbers 159972/2018-3)。
文摘The scale of forest and landscape restoration is expected to increase during the UN Decade on Ecosystem Restoration and its contribution to the provision of critical ecosystem services to society.Several models of forest restoration may improve ecosystem services,including soil organic carbon(SOC)storage.A review was carried out to access:(1)the variability of SOC storage between worldwide forest restoration models and,(2)the effects of climate,soil class,soil texture,and vegetation type on SOC storage.We reviewed 119 primary studies with information on SOC and soil texture for different forest restoration models.The restoration models were grouped into four categories:natural regeneration,monocultures,agroforestry,and mixed forest.SOC data was extracted from these four restoration models,other land uses(cropland,bare land,grassland,and natural forest),climate regimes,and soil properties.The SOC storage in the forest restoration models and other land uses at a global scale ranged between 0.1 to 514 Mg ha^(-1).The overall mean value for SOC storage was higher for natural regeneration(112 Mg ha^(-1)),followed by agroforestry(74 Mg ha^(-1)),mixed forest(73 Mg ha^(-1)),and monocultures(68 Mg ha^(-1)).However,the average SOC storage was similar among the four restoration models in the moist warm climate zone.The SOC storage mean value in the moist cool zone was 23%higher than the dry cool zone(81 and 62 Mg ha^(-1),respectively),and 50%higher for the moist warm zone when compared to the dry warm climatic zone(74 and 38 Mg ha^(-1),respectively).The SOC storage of the restoration models was positively related to soil depth(0.59;p<0.01),clay content(0.29;p<0.01),and stand age(0.17;p<0.01).Globally,the mean values of SOC storage were 26,66,and 139 Mg ha^(-1) at zero-10,zero-30,and zero-100 cm depths,respectively.In addition,sandy soils showed smaller mean values of SOC storage than medium to clay soils,especially in deeper soil layers.Furthermore,SOC storage was positively related between restoration models and other land uses(0.93;p<0.01),suggesting a prominent effect of climate and soil properties on SOC.Forest restoration models showed larger SOC storage when compared to croplands and bare land,but in general it was smaller or similar when compared to pasture and natural forest.
基金funded by the World Agroforestry Centre (ICRAF) through the Science Domains 1 (Agroforestry productivity) and 3 (Tree diversity, domestication and delivery)
文摘The variation in shoot and root seedling growth traits was compared among three Faidherbia albida （Del）. A. Chev. provenances originating from Kenya （Taveta）, Malawi （Bolero） and Ghana （Bolgatanga）; representing east, south and west Africa, respectively. Bulked seeds from three provenances were grown in two soil types （clay and sand） at the World Agroforestry Centre nursery, Nairobi. Seedlings grown in clay soil had high shoot growth and shoot to root ratios but shorter root length, lower number of nodules and specific root length compared to seedlings in sand soil. Shoot to root ratios reduced with time and this was more pronounced in sand soil. Overall, the Bolero and Taveta provenances had higher growth than the Bolgatanga provenance. This was probably because plants grown in nutrient-rich clay soil invest more in shoot growth as compared to root growth. Longer root growth in sand soil shows a better adaptive mechanism that increases competitive ability and survival in nutrient-poor systems. Variations observed among the seedling variables such us shoot and root growth could be used for early selection for reforestation and agroforestry in predominantly clay and sand soil areas.
文摘Small H-beams such as the No.14-20 I-steel can be inserted into soil-cement retaining walls to form small H-beam soil-cement compound walls, functioning both as a retaining wall and a cutoff wall for braced structure excavations. Being different from the mixed soil-cement wall （SMW）, the interaction between soil-cement and small H-steel is very good. We have carried out a series of bending experiments on small H-beams in soil-cement model compound beams to study the mechanism of interactions. The results show that the interaction between H-beams and soil-cement is very good, whether the H-beam is single or double. Joint forms of double H-beams at one end have little effect on both the contribution coefficient and on ultimate deflection before cracking. But after cracking, the joint forms greatly affect the contribution coefficient. We conclude that the rigid joint girder for double H-beams is a better choice in oractice.
