北长山岛森林乔木层碳储量及其影响因子

人工林是庙岛群岛典型的陆地生态系统的组成部分,对维护海岛地区生态环境具有重要作用。采用现有生物量相对生长方程和样地调查数据相结合的方法,以庙岛群岛中北长山岛为研究区,对海岛黑松纯林与黑松×刺槐混交林两种林型的碳储量进行了估算,并分析了土壤质地及其理化性质对海岛乔木层碳储量的影响。结果表明:黑松乔木层平均碳储量为84.00 t/hm²,接近于世界平均水平(86.00 t/hm²);黑松×刺槐混交林乔木层平均碳储量为29.60 t/hm²,高于山东省乔木层的平均碳储量(27.62 t/hm²)。应用因子分析法研究影响乔木层碳储量的主要因子,结果表明:土壤质地、pH值、含水量及含盐量是影响海岛乔木碳储量重要的影响因子。北长山岛土壤全氮、总磷、土壤有机质、碳氮比等其他理化性质对乔木层碳储量影响不是非常明显。     

Carbon pools recover more quickly than plant biodiversity in tropical secondary forests

Although increasing efforts are being made to restore tropical forests, little information is available regarding the time scales required for carbon and plant biodiversity to recover to the values associated with undisturbed forests. To address this knowledge gap, we carried out a meta-analysis comparing data from more than 600 secondary tropical forest sites with nearby undisturbed reference forests. Above-ground biomass approached equivalence to reference values within 80 years since last disturbance, whereas below-ground biomass took longer to recover. Soil carbon content showed little relationship with time since disturbance. Tree species richness recovered after about 50 years. By contrast, epiphyte richness did not reach equivalence to undisturbed forests. The proportion of undisturbed forest trees and epiphyte species found in secondary forests was low and changed little over time. Our results indicate that carbon pools and biodiversity show different recovery rates under passive, secondary succession and that colonization by undisturbed forest plant species is slow. Initiatives such as the Convention on Biological Diversity and REDD+ should therefore encourage active management to help to achieve their aims of restoring both carbon and biodiversity in tropical forests.     

碳离子辐照对菘蓝药性品质和分子水平的诱变效应

以野生菘蓝种子为材料,以不同剂量的碳离子(12 C6+)进行辐照处理(辐照剂量分别为30Gy、60Gy、90Gy、120Gy),分析12 C6+辐照对菘蓝种子萌发、幼苗生长、主要药用成分含量及其基因和蛋白质多态性变化的影响,为菘蓝品质育种、分子生物学研究和重离子辐照诱变的应用提供依据。结果显示:(1)12 C6+辐照处理后菘蓝的成苗率和根鲜重均随辐照剂量增加而逐步显著降低,其中30Gy处理对菘蓝生长抑制程度最小,但处理后菘蓝根中的主要药效成分4(3H)喹唑酮和靛玉红的含量增加幅度最大且最高,分别为野生型的2.2倍和2.3倍。(2)SRAP分子标记分析表明,菘蓝基因组的变异度随着辐照强度的增强而增大,其中30Gy处理的突变体与野生型相比有33.59%的多态性变异。(3)SDS-PAGE考马斯亮蓝染色和磷酸化染色分析表明,菘蓝的总蛋白和磷酸化蛋白表达水平均随辐照剂量变化出现了不同程度的改变,但并不与辐照强度呈正相关,说明植物在防御重离子辐照伤害时存在补偿机制。研究发现,30Gy的12 C6+辐照是菘蓝诱变的最佳剂量,能够显著提高其有效成分的含量,为优质菘蓝诱变育种奠定了基础。     

Responses of soil labile organic carbon and water-stable aggregates to reforestation in southern subtropical China

中国南亚热带土壤易分解有机碳和水稳性团聚体对造林的响应 造林被认为可以提高土壤碳稳定性并促进土壤碳累积。然而,实验结果差异很大,造林在提高土壤碳稳定性方面的作用仍存在争议。因此,在森林生态系统中不同土壤碳库对造林如何响应目前尚不清楚。基于此,本文对亚热带地区的尾叶桉林(Eucalyptus urophylla)、厚荚相思林(Acacia crassicarpa)、 红锥林(Castanopsis hystrix)、10树种混交林和自然恢复草坡等5种不同林型的土壤碳组分进行了研究,评估其不同土层(0–10、10–20、20–40 和40–60 cm)中的土壤易分解有机碳(容易被高锰酸钾氧化的有机碳ROC和土壤可溶性有机碳DOC)及土壤团聚体相关的碳对造林的响应。实验结果表明,造林(与自然恢复草坡比较)和林型并没有显著影响土壤ROC浓度,而自然恢复草坡土壤的DOC浓度在4个土层中均最高。0–10 cm土层中各径级的土壤团聚体其碳(C)浓度均是红锥林最高。此外,在任一土层中,林型对不同径级土壤水稳性团聚体比例的影响均不显著。但是土壤深度显著改变土壤团聚体的分布,0–20 cm土层主要为>0.25 mm粒径的团聚体,20–60 cm土层则是0.053–2 mm粒径的团聚体占主导。这些结果显示造林和林型影响土壤DOC 和团聚体C,而且它们相比于ROC对造林的响应更为敏感。研究发现,与自然恢复相比,人工林降低了土壤DOC浓度,暗示它可能会减少土壤C的淋溶损失。此外,红锥林能够通过物理保护提高表土层中土壤碳的稳定性。本研究为关注土壤碳汇功能时的中国南亚热带地区造林树种选择提供了有价值的信息。     

Wildfire Smoke,Fire Management,and Human Health

Burning landscapes under controlled conditions to reduce the risk of wildfires is a controversial land management practice. The health risks of smoke generated from controlled burning relative to wildfire remain uncertain. Recent work in the Australian monsoon tropics provided a unique opportunity to study the health effects of smoke pollution at and well below national air quality standards. It found that for each increase in the atmospheric mass of particles 10 g or less in aerodynamic diameter (PM₁₀) per cubic meter of air per 24-hour period, there was a 26% increase in daily asthma presentations to the emergency department of the Royal Darwin Hospital, with an apparent threshold at 40 g/m³ PM₁₀ (lower than the Australian PM₁₀ air quality standard of 50 g/m³). This finding was unaffected by adjusting for weekly rates of influenza, weekday vs. weekends, and school holiday periods. Although further research is being undertaken to substantiate these findings, the upshot of the study suggests that for airsheds containing large human populations, fire managers should strive to keep smoke pollution less than 40 g/m³ PM₁₀.     

Photosynthetic performance of vegetative and reproductive structures of green hellebore (<Emphasis Type="Italic">Helleborus viridis</Emphasis> L. agg.)

Photosynthetic irradiance response of vegetative and reproductive structures of the green-flowered deciduous perennial green hellebore was studied by the comparative use of chlorophyll (Chl) fluorescence techniques and gas exchange measurements. All the Chl-containing organs (leaves, sepals, stalks, and fruits) examined were photosynthetically active showing high intrinsic efficiencies of photosystem 2 (F_v/F_m: 0.75–0.79) after dark adaptation. Even in the smaller fertile and sterile parts of the flower (nectaries and anthers) a remarkable photosynthetic competence was detected. With increasing photon flux densities (PFD) electron transport rates, actual quantum yields, and photochemical quenching coefficients of the main photosynthetic organs decreased in the order: leaf>sepal>fruit>stalk. At moderate to high PFDs the sepals achieved maximum electron transport rates corresponding to about 80 % of concomitant mature leaves. In contrast, maximum net photosynthetic rate of the sepals [2.3 mol(CO₂) m^–2 s^–1] were less than one fourth of the leaves [10.6 mol(CO₂) m^–2 s^–1]. This difference is explained by a 70–80 % lower stomatal density of sepals in comparison to leaves. As the basal leaves emerge late during fruit development, the photosynthetically active sepals are a major source of assimilates, contributing more than 60 % of whole-plant CO₂ gain in early spring. The ripening dehiscent fruits are characterized by an effective internal re-fixation of the respirational carbon loss and thus additionally improve the overall carbon budget.     

祁连山典型流域谷地植被斑块演变与土壤性状

植物群落演变与土壤性状变化之间的相互作用和过程研究对于认识生态系统结构和功能演变有着重要的意义.对祁连山谷地灌丛草甸退化演变过程中植物群落物种组成、土壤物理和化学性状特征、及土壤与植被的相互作用进行了研究,结果表明,在祁连山谷地阴坡林线以下较小的空间范围,植被斑块由金露梅群落向金露梅-马蔺群落斑块和马蔺群落斑块演变,植被盖度降低,但物种多样性增加.不同植被斑块之间土壤水分有显著的梯度变化,土壤水分的变化导致植被的退化演替.植被斑块的演变导致土壤性状的明显分异,从金露梅灌丛斑块向金露梅-马蔺群落斑块和马蔺群落斑块演变,土壤容重显著增加,土壤团聚体组成由大粒级的大团聚体(》1mm)破碎为小粒级的大团聚体(1-0.25mm)和微团聚体(《0.25mm),团聚体稳定性降低,表明土壤结构的退化;土壤有机碳含量下降了31.2%和55.9%,干筛各粒级土壤团聚体中有机碳含量金露梅-马蔺群落斑块和马蔺群落斑块显著低于金露梅斑块,土壤团聚体平均重量粒径与有机碳含量存在显著相关,植被退化演变中土壤有机碳的损失部分地由于团聚体的破碎引起;土壤全氮和有效氮不同斑块之间也有显著的差异,植被斑块退化演变使氮的有效性降低;但磷、钾养分对植被变化的响应不敏感.植被的退化演变使土壤团聚体破碎、土壤结构退化,有机碳和全氮含量下降,使其抗侵蚀能力和水源涵养功能显著降低,又进一步加速植被的退化演替.在气候变暖的趋势下,马蔺斑块将进一步向林线逼近,灌丛草甸植被将会进一步退化和萎缩.