Understanding how ecological differences and anthropogenic disturbances synergistically drive population dynamics decline is critical for optimal management strategy definition. Main anthropogenic disturbances such as...Understanding how ecological differences and anthropogenic disturbances synergistically drive population dynamics decline is critical for optimal management strategy definition. Main anthropogenic disturbances such as habitat size reduction, fire and non-timber forest harvest affect demographic processes but our understanding of their interaction effects in contrasted ecological conditions is limited. We investigated the interaction effects of fruit harvest, fire, gallery forest size and distance to streambed on density, recruitment, survival and growth of Pentadesma butyracea offspring in dry and moist ecological conditions. We randomly selected in each ecological region six P. butyracea populations. We then established in each population, 10 subplots of 100 m2 within 1 ha to assess offspring demographic performance from 2015 to 2017. Results showed that fire suppressed the positive effect of large habitat size and amplified the negative effect of increasing local aridity on offspring growth. Fire and harvest synergistically reduced growth whereas offspring growth was resilient to fire in moist ecological region. Moist ecological conditions mitigated the negative effect of harvest on growth. Harvest mitigated the surprise negative effect of large habitat size on survival. However, in large gallery size, high harvest limited clonal recruitment and growth. There was a positive interaction effect between harvest and distance to streambed on survival (High harvest, Z = 2.045, p = 0.041, Medium, Z = 2.060, p = 0.039) but a negative interaction effect on growth (High, t = -2.357, p 0.05). Clonal offspring grew faster than sexual offspring in high harvest populations. In moist region, offspring survived better in large gallery forest size. In 2017, survival and growth were lower in large gallery forest. In 2017, offspring growth was higher near the riverbed where the survival rate low. This study suggests that management strategies should consider the interaction effects of anthropogenic disturbances and climatic condi展开更多
Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased subst...Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k（growth coefficient） and t_0（zero-length age） gradually increased from 0.26 and –0.58 year in 1960 to 0.56 and –0.25 year in 2008, respectively. Although, L∞（body length）sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t_r（inflexion age） decreased from 3.78 year in1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as： fishing vessel power〉feeding grade〉sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.展开更多
文摘Understanding how ecological differences and anthropogenic disturbances synergistically drive population dynamics decline is critical for optimal management strategy definition. Main anthropogenic disturbances such as habitat size reduction, fire and non-timber forest harvest affect demographic processes but our understanding of their interaction effects in contrasted ecological conditions is limited. We investigated the interaction effects of fruit harvest, fire, gallery forest size and distance to streambed on density, recruitment, survival and growth of Pentadesma butyracea offspring in dry and moist ecological conditions. We randomly selected in each ecological region six P. butyracea populations. We then established in each population, 10 subplots of 100 m2 within 1 ha to assess offspring demographic performance from 2015 to 2017. Results showed that fire suppressed the positive effect of large habitat size and amplified the negative effect of increasing local aridity on offspring growth. Fire and harvest synergistically reduced growth whereas offspring growth was resilient to fire in moist ecological region. Moist ecological conditions mitigated the negative effect of harvest on growth. Harvest mitigated the surprise negative effect of large habitat size on survival. However, in large gallery size, high harvest limited clonal recruitment and growth. There was a positive interaction effect between harvest and distance to streambed on survival (High harvest, Z = 2.045, p = 0.041, Medium, Z = 2.060, p = 0.039) but a negative interaction effect on growth (High, t = -2.357, p 0.05). Clonal offspring grew faster than sexual offspring in high harvest populations. In moist region, offspring survived better in large gallery forest size. In 2017, survival and growth were lower in large gallery forest. In 2017, offspring growth was higher near the riverbed where the survival rate low. This study suggests that management strategies should consider the interaction effects of anthropogenic disturbances and climatic condi
基金The National Basic Research Program(973 Program)of China under contract No.2015CB453303the Aoshan Scientific and Technical Innovation Program under contract No.2015ASKJ02-05the Taishan Scholar Project Special Fund
文摘Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k（growth coefficient） and t_0（zero-length age） gradually increased from 0.26 and –0.58 year in 1960 to 0.56 and –0.25 year in 2008, respectively. Although, L∞（body length）sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t_r（inflexion age） decreased from 3.78 year in1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as： fishing vessel power〉feeding grade〉sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.
