Wood {delta}13C, {delta}18O and radial growth responses of residual red pine to variable retention harvesting.
Wood {delta}13C, {delta}18O and radial growth responses of residual red pine to variable retention harvesting.
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DOI：
10.1093/treephys/tpp119
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发表时间：
2010-03
期刊：
影响因子：
4
通讯作者：
M. Powers;K. Pregitzer;B. Palik;C. Webster
中科院分区：
文献类型：
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作者：
M. Powers;K. Pregitzer;B. Palik;C. Webster
可变保留采伐被用来通过保留采伐前生态系统中的活树和其他结构遗产来促进受管理森林结构复杂性的发展。虽然收获应该会增加残留树木的资源可获得性，但更大的树冠暴露也可能增加环境压力，这使得很难预测不同结构环境下的生长。采用红松树(Pinus resinosa Ait.)年轮的稳定碳同位素比值(Delta(13)C)。作为内在水分利用效率(IWUE)的一个指标，光合碳同化(A)与气孔导度(g(S))的比值，以更好地了解残留物在收获后的生长反应中的差异，残留物在小(0.1ha)林隙之间分散、聚集或在大(0.3ha)林隙之间聚集。以稳定氧同位素比值(δ(18)O)作为g(S)的指标，以探讨i WUE变化背后的驱动因素。与未采伐对照林相比，保留采伐对林分尺度上的Delta(13)C或Delta(18)O似乎没有影响，但在采伐后第二年和第三年，剩余树木Delta(13)C与样地断面积之间存在显著的负相关，这表明iWUE随着覆盖层竞争的加剧而下降。残留树三角洲(18)O在不同处理和不同基准区之间相似。从处理前到处理后的测量期，不同保留采伐的树木的径向生长显示出小幅但正的增长，而未采伐的对照林分的径向生长则下降。不同保留处理间径向生长差异不显著。我们的结果表明，相对开放环境中的残留红松受益于较大的A，但没有显示出g(S)变化的证据，这表明水关系发生了变化。
Variable retention harvests are used to enhance the development of structural complexity in managed forests by retaining living trees and other structural legacies from the pre-harvest ecosystem. While harvesting should increase resource availability to residual trees, greater crown exposure may also increase environmental stress, which makes it difficult to predict growth in different structural environments. We used stable carbon isotope ratios (delta(13)C) of annual rings from red pine trees (Pinus resinosa Ait.) as an index of intrinsic water use efficiency (iWUE), the ratio of photosynthetic carbon assimilation (A) to stomatal conductance (g(s)), to better understand how differences in physiological performance relate to growth responses following harvests that left residuals dispersed, aggregated between small (0.1 ha) gaps or aggregated between large (0.3 ha) gaps. Stable oxygen isotope ratios (delta(18)O) were used as an index of g(s) to investigate the drivers behind changes in iWUE. Retention harvesting did not appear to affect delta(13)C or delta(18)O at the stand scale when compared to unharvested control stands, but there was a significant, negative correlation between residual tree delta(13)C and plot basal area in the second and third years after harvesting that suggests declining iWUE as overstory competition increases. Residual tree delta(18)O was similar across treatments and basal areas. Trees in variable retention harvests showed small but positive increases in radial growth from the pre-treatment to post-treatment measurement periods, while radial growth declined in unharvested control stands. There were no significant differences in radial growth among retention treatments. Our results suggest residual red pine in relatively open environments benefit from greater A but do not show evidence of changes in g(s) that would indicate altered water relations.