STABILITY IN THE PLANT-COMMUNITIES OF THE PARK-GRASS-EXPERIMENT - THE RELATIONSHIPS BETWEEN SPECIES RICHNESS, SOIL-PH AND BIOMASS VARIABILITY
STABILITY IN THE PLANT-COMMUNITIES OF THE PARK-GRASS-EXPERIMENT - THE RELATIONSHIPS BETWEEN SPECIES RICHNESS, SOIL-PH AND BIOMASS VARIABILITY
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DOI：
10.1098/rstb.1994.0140
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发表时间：
1994-10-29
影响因子：
6.3
通讯作者：
CRAWLEY, M
中科院分区：
文献类型：
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作者：
DODD, ME;SILVERTOWN, J;CRAWLEY, M
公园草实验 (PGE) 于 1856 年在洛桑实验站开始，至今仍在运行，为测试一系列可比较的植物群落中物种数量和土壤反应对生物量变异的影响提供了独特的机会。通过计算十一年移动窗口中年干草产量随时间变化的变异系数（CV）来测量生物量变异性。 CV和物种数均与生物量呈强负相关；这两种关系都受到时间和 pH 值的影响。 1862 年至 1991 年间的 42 年中，CV 对非酸化地块的物种数量和平均生物量的多元回归表明，生物量和 CV 之间存在负相关关系，在大多数年份中呈负相关，并且在近四分之三的年份中显着如此 (30/42)。我们无法判断这种影响有多少是生物量平均值和 CV 之间的统计关系所固有的。在 29/42 年中，物种数量与 CV 呈负相关，但这仅在 3 次情况下具有统计显着性。由于这种关系在我们拥有最大样本量（34 个地块）的年份（1991 年）非常显着，因此我们初步得出结论，物种丰富的群落中生物量变异性可能较低，尽管这种影响可能较弱。我们认为，低 pH 值带来的生理压力可以解释酸化土壤地块的更大变异性。随着时间的推移，各小区生物量变异性的增加可能部分归因于整个实验的酸化。提出了三个假设来解释物种丰富度和生物量变异性之间的关系：（i）物种丰富地块上的生物量变异性可以更好地缓冲气候变化，因为物种对气候条件的反应不同：（ii）生物量变异性较大的地块上的物种较少，因为在生物量达到高值的年份，物种因竞争排斥而消失； (iii) 物种丰富度和变异性均与第三个变量相关，例如地块内的土壤水分不足。所有三个假设都可以在 PGE 内进行测试。
The Park Grass Experiment (PGE), begun at Rothamsted Experimental Station in 1856 and still running, affords a unique opportunity to test for the influence of species number and soil reaction on biomass variability in a suite of comparable plant communities. Biomass variability was measured by calculating the coefficient of variation (CV) over time of annual hay yield in an eleven-year moving window. CV and species number were both strongly negatively correlated with biomass; both relations were affected by time and pH. Multiple regression of CV on species number and mean biomass for non-acidified plots in 42 years between 1862 and 1991 showed a relationship between biomass and CV which was negative in most years and significantly so in nearly three quarters of them (30/42). We are unable to tell how much of this effect is intrinsic to the statistical relation between the mean and CV of biomass. Species number was negatively correlated with CV in 29/42 years, but this was statistically significant on only three occasions. Because this relation was highly significant in the year (1991) for which we have the largest sample size (34 plots), we tentatively conclude that biomass variability may be lower in more species-rich communities, although the effect is possibly a weak one. We suggest that physiological stresses imposed by low pH may explain the greater variability of plots with acidified soil. An increase in the variability of biomass that occurred across plots with time may be due in part to acidification across the whole experiment. Three hypotheses are proposed to explain the relationship between species richness and biomass variability: (i) biomass variability on more species-rich plots is better buffered against climatic variation because species differ in their response to climatic conditions: (ii) there are fewer species on plots with greater biomass variability because species have been lost by competitive exclusion in years when biomass reaches high values; (iii) species richness and variability are both correlated with a third variable, for example soil moisture deficit within a plot. All three hypotheses are susceptible to testing within the PGE.