Plant Functional Traits Indicate Forest Ecosystem Services

Humankind benefits in a multitude of ways from ecosystems. Collectively, these benefits are known as ecosystem services. In recent years, the connotation and quantitative evaluation of ecosystem services has become the leading subject of ecology. Plant functional traits are the plant physiological characteristics which can respond to the changes of the living environment and (or) have a certain impact on the ecosystem structure and function. Also, functional traits can reflect the role of plants in indicating the structure and function of ecosystem. Coincidentally, the forest ecosystem services are generated and decided by the process and function of ecosystem. Therefore, using functional traits as indicators to evaluate forest ecosystem services directly may be a good way, comparing to the other assessment methods. Based on this, we took3kinds of ecosystem services as example, including water conservation, carbon sequestration and windproof of the forest, to verify the role of functional traits in indicating forest ecosystem services and to screen the indicative functional traits of the3kinds of ecosystem services respectively. In this study, an investigation was made on more than15functional traits in13different types (3successional series and4natural windbreaks) of forest communities in Ningbo region (Tiantong, Shuangfeng, Xiangshan), Zhejiang Province. Meanwhile, we explored how the forest ecosystem services shift during community succession and revealed the change pattern of windproof ability of4communities on different distances from the shoreline.The main results are as follows:1) The attenuation coefficient of community wind speed (Ca) was used as a measure to evaluate the windproof services, and leaf intensity (LI), leaf size (LS), specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (LT), petiole length (PL), petiole thickness (PT), tree height (H), basal diameter (BD), wood density (WD), crown length ratio (CL/H), crown diameter ratio (CD/H) were treated as the functional traits studied. We figured out the community weighted mean of the functional traits (CWM) and analyzed the relationship between Ca and functional traits. It was found that H, BD, LS, SLA and PT were significantly positive correlated with Ca (Y)(P<0.05), and LDMC, LI were significantly negative correlated with Ca (Y)(P<0.05). Thus, the functional traits above may be the indicators of windproof services of forest ecosystem. An evaluation equation of forest windproof services were built based on functional traits after stepwise regression, Y=0.987+0.037H+0.001SLA-0.008LDMC-0.118CL/H-0.0002LI (R2=0.99, P<0.001).2) The maximum net photosynthetic rate of community (Pmax) was regarded as the index to assess the carbon sequestration services of the forest, and leaf size (LS), specific leaf area (SLA), leaf dry matter content (LDMC), tree height (H), basal diameter (BD), wood density (WD), crown length ratio (CL/H), transpiration rate (Tr) and stomatal conductance (Cond) were the functional traits studied. The results showed that both Cond and Tr had significantly positive relationship with Pmax(Y)(P<0.0S), and CA was significantly negative correlated with Pmax(Y)(P<0.05). Thus, the functional traits above can indicate carbon sequestration services very well. An evaluation equation of forest carbon sequestration services were built based on functional traits after stepwise regression, Y=0.230+3.114Tr-0.049BD-1.609CL/H (R2=0.99, P<0.001).3) In this study, saturated water capacity (Ws), the sum of non-capillary storage capacity and capillary storage capacity, was used as a measure of the capacity of forest soil water conservation. The tree height, leaf size, transpiration rate and other10plants foliage characteristics were considered as the functional traits of community. The findings were:(a) As to the soil layer (0-20cm), H, CA, and LDMC showed significantly positive relationship with Ws(Y)(P<0.05), while Pmax and Tr were significantly negative correlated with Ws (P<0.05);(b) As to the soil layer (20-40cm), CA showed significantly positive relationship with Ws (P<0.05). Similar to (a), both Pmax and Cond have significantly negative relationship with Ws (P<0.05). Therefore, H, CA, LDMC, Pmax and Cond have been picked out as the functional indicators to indicate the capacity of forest soil water conservation. The corresponding regression models were:(a)0-20cm:Y=76.479+4.006H+4.378LDMC (R2=0.97, P<0.01);(b)20-40cm:Y=316.589-14.778Pmax (R2=0.93, P<0.01). 4) Windproof, water conservation, carbon sequestration were main content of ecosystem services. Based on the results1)-3), with the approach of analytic hierarchy process (AHP), unifying windproof, water conservation, carbon sequestration together, we built an evaluation system to evaluate ecosystem services. It was found that (a) For theforest in hilly areas, the ability of carbon sequestration of Tiantong was more prominent than Shuangfeng and Nanshan; the ability of water conservation of Tiantong and Shuangfeng were greater than the other two;(b) For the communities in different successional stages, the ability of water conservation of the community in later successional stage was greater, however, the ability of carbon sequestration of the community in later successional stage was smaller than the other two stages,(c) For the coastal forest, the windproof ability of the forest community which is closest to the shore line was greatest among the others.5) Ecosystem services also shifted with the community dynamics of succession. The carbon sequestration capacity of the community in early successional stage was significantly more obvious than the mid-and-late successional communities (P<0.05). For the top soil, the saturated water capacity (Ws) of the community in mid-and-late successional stage was significantly greater than the early successional communities (P<0.05). For deep soil, the saturated water capacity (Ws) increased with succession, but the trend was not significant.6) Developmental stages of forest communities in the island region tend not to be so obvious, so only4natural forest windbreaks were studied in this research. The results were that with the increase of the distance from the coast, the capacity of forest windproof gradually increased, which may be caused by the changing pattern of functional traits under different wind stress intensity.