Ryan Michael G, Hubbard Robert M, Clark Deborah A, Sanford Robert L
BDA Forest Service, Rocky Mountain Experiment Station, 240 West Prospect Street, 80526-2098, Fort Collins, CO, USA.
Organization for Tropical Studies, Apartado 676.2050, San Pedro, Costa Rica.
Oecologia. 1994 Dec;100(3):213-220. doi: 10.1007/BF00316947.
We measured CO efflux from stems of two tropical wet forest trees, both found in the canopy, but with very different growth habits. The species were Simarouba amara, a fast-growing species associated with gaps in old-growth forest and abundant in secondary forest, and Minquartia guianensis, a slow-growing species tolerant of low-light conditions in old-growth forest. Per unit of bole surface, CO efflux averaged 1.24 μmol m s for Simarouba and 0.83 μmol ms for Minquartia. CO efflux was highly correlated with annual wood production (r =0.65), but only weakly correlated with stem diameter (r =0.22). We also partitioned the CO efflux into the functional components of construction and maintenance respiration. Construction respiration was estimated from annual stem dry matter production and maintenance respiration by subtracting construction respiration from the instantaneous CO flux. Estimated maintenance respiration was linearly related to sapwood volume (39.6 μmol ms at 24.6° C, r =0.58), with no difference in the rate for the two species. Maintenance respiration per unit of sapwood volume for these tropical wet forest trees was roughly twice that of temperate conifers. A model combining construction and maintenance respiration estimated CO very well for these species (r =0.85). For our sample, maintenance respiration was 54% of the total CO efflux for Simarouba and 82% for Minquartia. For our sample, sapwood volume averaged 23% of stem volume when weighted by tree size, or 40% with no size weighting. Using these fractions, and a published estimate of aboveground dry-matter production, we estimate the annual cost of woody tissue respiration for primary forest at La Selva to be 220 or 350 g C m year, depending on the assumed sapwood volume. These costs are estimated to be less than 13% of the gross production for the forest.
我们测量了两种热带湿润森林树木树干的二氧化碳排放通量，这两种树都生长在树冠层，但生长习性差异很大。这两个物种分别是苦木科的苦木，一种生长迅速的物种，与老龄森林中的林窗有关，在次生林中数量丰富；以及圭亚那苦木，一种生长缓慢的物种，能耐受老龄森林中的弱光条件。按单位树干表面积计算，苦木的二氧化碳排放通量平均为1.24微摩尔·米⁻²·秒⁻¹，圭亚那苦木为0.83微摩尔·米⁻²·秒⁻¹。二氧化碳排放通量与年木材产量高度相关（r = 0.65），但与树干直径的相关性较弱（r = 0.22）。我们还将二氧化碳排放通量划分为用于构建和维持呼吸作用的功能组分。构建呼吸作用是根据年树干干物质产量估算的，维持呼吸作用则是通过从瞬时二氧化碳通量中减去构建呼吸作用来估算。估算出的维持呼吸作用与边材体积呈线性相关（在24.6℃时为39.6微摩尔·米⁻²·秒⁻¹，r = 0.58），两个物种的速率没有差异。这些热带湿润森林树木单位边材体积的维持呼吸作用大约是温带针叶树的两倍。一个结合了构建呼吸作用和维持呼吸作用的模型对这些物种的二氧化碳排放通量估算得非常好（r = 0.85）。对于我们的样本，维持呼吸作用占苦木总二氧化碳排放通量的54%，占圭亚那苦木的82%。对于我们的样本，边材体积按树木大小加权时平均占树干体积的23%，不加大小权重时为40%。利用这些比例以及已发表的地上干物质产量估算值，我们估计拉塞尔瓦原始森林中木质组织呼吸作用的年成本为220或350克碳·米⁻²·年，这取决于假设的边材体积。据估计，这些成本不到森林总生产量的13%。
