Fagundes Marina, Weisser Wolfgang, Ganade Gislene
Restoration Ecology Research Group Department of Ecology Universidade Federal do Rio Grande do Norte Natal RN Brazil.
Terrestrial Ecology Research Group Department of Ecology and Ecosystem Management School of Life Sciences Weihenstephan Technical University of Munich Freising Germany.
Ecol Evol. 2018 Apr 27;8(10):5173-5184. doi: 10.1002/ece3.3962. eCollection 2018 May.
Plant establishment is a challenge in semiarid environments due to intense and frequent drought periods. The presence of neighboring trees (nurses) can increase the establishment of seedlings (targets) by improving resource availability and microclimate. The nurse effect, however, might vary depending on nurse-target species combinations but factors that predict this specificity are poorly known. We used a multispecies experiment to investigate the facilitation potential of trees from a range of successional stages, focusing on how nurse functional traits can predict species-specific interaction outcomes. We conducted a factorial field experiment in a Brazilian semiarid tropical forest during a severe drought period. Sixty pairs of interacting tree species, 20 potential nurses, and three targets were used. Seedlings of all targets were planted both under and far from the nurse canopy, in a randomized block design replicated five times. Target growth and survival were monitored for 275 days from the beginning of the dry season, and interaction outcomes were calculated using the Relative Interaction Intensity (RII) index. Nurse functional traits such as successional stage, height, wood density, and canopy diameter were used as explanatory variables to predict RII values. The average effect of nurse species on target plants was in general positive, that is, seedling survival and growth increased under the nurse canopy. However, for growth pairwise interactions were significantly species specific. Successional stage was the only functional trait explaining RII values, with pioneer tree species being stronger facilitators than later successional trees. However, the explanation power of this variable was low, and positive, negative, or neutral interactions were found among nurse trees of all successional stages. Because seedling mortality during drought in semiarid systems is high, future studies should investigate how nurse traits related to water use could influence nurse facilitation skills.
由于干旱期强烈且频繁，在半干旱环境中植物定植是一项挑战。邻近树木（护树）的存在可通过改善资源可用性和微气候来提高幼苗（目标树）的定植率。然而，护树效应可能因护树 - 目标树物种组合而异，但预测这种特异性的因素却鲜为人知。我们进行了一项多物种实验，以研究一系列演替阶段树木的促进潜力，重点关注护树功能性状如何预测物种特异性的相互作用结果。在巴西半干旱热带森林的严重干旱期，我们进行了一项析因田间实验。使用了60对相互作用的树种、20种潜在护树和3种目标树。所有目标树的幼苗都种植在护树树冠下和远离护树树冠的地方，采用随机区组设计，重复5次。从旱季开始对目标树的生长和存活进行了275天的监测，并使用相对相互作用强度（RII）指数计算相互作用结果。将护树的功能性状如演替阶段、高度、木材密度和树冠直径用作解释变量来预测RII值。护树物种对目标植物的平均效应总体上是积极的，也就是说，在护树树冠下幼苗的存活和生长增加。然而，对于生长而言，成对相互作用具有显著的物种特异性。演替阶段是解释RII值的唯一功能性状，先锋树种比后期演替树种具有更强的促进作用。然而，该变量解释力较低，并且在所有演替阶段的护树之间都发现了正、负或中性相互作用。由于半干旱系统中干旱期间幼苗死亡率很高，未来的研究应调查与水分利用相关的护树性状如何影响护树的促进技能。
